Reconstituted substrate structure and fabrication methods for heterogeneous packaging integration

ABSTRACT

The present disclosure relates to thin-form-factor reconstituted substrates and methods for forming the same. The reconstituted substrates described herein may be utilized to fabricate homogeneous or heterogeneous high-density 3D integrated devices. In one embodiment, a silicon substrate is structured by direct laser patterning to include one or more cavities and one or more vias. One or more semiconductor dies of the same or different types may be placed within the cavities and thereafter embedded in the substrate upon formation of an insulating layer thereon. One or more conductive interconnections are formed in the vias and may have contact points redistributed to desired surfaces of the reconstituted substrate. The reconstituted substrate may thereafter be integrated into a stacked 3D device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/870,843, filed May 8, 2020, which claims priority to Italian patentapplication number 102019000006736, filed May 10, 2019, each of which isherein incorporated by reference in its entirety.

BACKGROUND Field

Embodiments of the present disclosure generally relate to the field ofsemiconductor device manufacturing, and more particularly, to structuresand methods of packaging semiconductor devices.

Description of the Related Art

The ever-increasing demand for miniaturized semiconductor devices hasled to continuously increasing circuit densities and decreasing devicesizes. As a result of the continued scaling of these devices, integratedcircuits have evolved into complex 3D devices that can include millionsof transistors, capacitors, and resistors on a single chip. 3Dintegration allows a significant reduction in device footprint andenables ever shorter and faster connections between that device'ssub-components, thus improving processing capabilities and speedthereof. These capabilities make 3D integration a desirable techniquefor the semiconductor device industry to keep pace with Moore's law.

Currently, the 3D device technology landscape includes several generalclasses of 3D integration processes that vary in the level at which thedevices are partitioned into different pieces. Such 3D integrationprocesses include stacked integrated circuit (“SIC”) technology,system-in-package (“SiP”) technology, and system-on-chip (“SOC”)technology. SIC devices are formed by stacking individual semiconductordies on top of one another. Currently, such SIC devices are achieved bydie-to-interposer stacking or die-to-wafer stacking approaches. SiPdevices, on the other hand, are formed by stacking packages on top ofone another, or by integrating multiple semiconductor dies or devices ina single package. Current approaches to fabricate SiP devices includepackage-to-package reflow and fan-out wafer level packaging. Lastly,SOCs realize higher density by heterogeneously stacking severaldifferent functional partitions of a circuit. Conventionally, thesefunctional circuit partitions are stacked through wafer-to-wafer bondingtechniques.

Despite the promise of 3D device technology, current approaches to 3Dintegration face many challenges. One of the major drawbacks associatedwith current 3D integration techniques and particularly SiP fabricationprocesses is sub-optimal thermal management. As a result of the thermalproperties of the molding compound materials utilized duringconventional packaging manufacturing processes, coefficient of thermalexpansion (“CTE”) mismatch may occur between the molding compound andany integrated semiconductor device components (e.g., semiconductordies). The existence of CTE mismatch may cause undesirable repositioningof device components and warpage of wafers and/or even entire integratedpackages, thus inducing misalignment between device contacts and viainterconnects in any subsequently formed redistribution layers.

Accordingly, there is a need in the art for improved methods of formingreconstituted substrates for packaging schemes.

SUMMARY

The present disclosure generally relates to device packaging processes,and in particular, relates to methods of forming a reconstitutedsubstrate for advanced 3D packaging applications.

In one embodiment, a method of forming a 3D integrated semiconductordevice includes positioning a first semiconductor die within at leastone cavity formed in a first substrate; disposing a first flowablematerial over a first surface and a second surface of the firstsubstrate, the first flowable material filling voids formed betweensurfaces of the semiconductor die and surfaces of the at least onecavity in the first substrate, the first flowable material furtherdisposed on a surface of at least one via formed through the firstsubstrate; forming a first conductive layer in the at least one viathrough the first substrate, the first flowable material disposedbetween the first conductive layer and the surface of the at least onevia through the first substrate; disposing a second flowable materialover a surface of the first flowable material, the second flowablematerial integrating with the first flowable material; positioning asecond substrate on the second flowable material, the second substratehaving at least one cavity and at least one via formed therein;positioning a second semiconductor die within the at least one cavityformed in the second substrate; disposing a third flowable material overan exposed surface of the second substrate, the third flowable materialfilling voids formed between surfaces of the second semiconductor dieand surfaces of the at least one cavity in the second substrate, thethird flowable material integrating with the second flowable material;and forming a second conductive layer in the at least one via throughthe second substrate, the third flowable material disposed between theconductive layer and the surface of the at least one via through thesecond substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, and may admit to other equally effective embodiments.

FIG. 1 illustrates a flow diagram of a process for forming areconstituted substrate, according to embodiments described herein.

FIG. 2 illustrates a flow diagram of a substrate structuring processduring formation of a reconstituted substrate, according to embodimentsdescribed herein.

FIGS. 3A-3E schematically illustrate cross-sectional views of asubstrate at different stages of the substrate structuring processdepicted in FIG. 2.

FIGS. 4A-4B illustrate schematic top views of substrates structured withthe processes depicted in FIGS. 2 and 3A-3E according to embodimentsdescribed herein.

FIG. 5 illustrates a flow diagram of a process for forming anintermediary die assembly having through-assembly vias and contactholes, according to embodiments described herein.

FIGS. 6A-6K schematically illustrate cross-sectional views of theintermediary die assembly at different stages of the process depicted inFIG. 5.

FIG. 7 illustrates a flow diagram of a process for forming anintermediary die assembly having through-assembly vias and contactholes, according to embodiments described herein.

FIGS. 8A-8G schematically illustrate cross-sectional views of theintermediary die assembly at different stages of the process depicted inFIG. 7.

FIG. 9 illustrates a flow diagram of a process for forminginterconnections in an intermediary die assembly, according toembodiments described herein.

FIGS. 10A-10K schematically illustrate cross-sectional views of theintermediary die assembly at different stages of the interconnectionformation process depicted in FIG. 9.

FIG. 11 illustrates a flow diagram of a process for forming aredistribution layer on a reconstituted substrate followed bysingulation, according to embodiments described herein.

FIGS. 12A-12N schematically illustrate cross-sectional views of areconstituted substrate at different stages of forming a redistributionlayer followed by singulation, as depicted in FIG. 11.

FIG. 13 illustrates a flow diagram of a process for forming a stacked 3Dstructure integrating a reconstituted substrate by build-up stacking,according to embodiments described herein.

FIGS. 14A-14D schematically illustrate cross-sectional views of astacked 3D structure at different stages of build-up stacking, asdepicted in FIG. 13.

FIG. 15A-15C schematically illustrate cross-sectional views ofstructures incorporating dynamic random access memory (DRAM) stacksformed by the process depicted in FIG. 13, according to embodimentsdescribed herein.

FIG. 16 schematically illustrates a stacked 3D structure integrating areconstituted substrate, according to embodiments described herein.

FIGS. 17A-17B schematically illustrate stacked 3D structures integratinga reconstituted substrate, according to embodiments described herein.

FIG. 18 schematically illustrates cross-sectional views of dynamicrandom access memory (DRAM) stacks formed by processes described herein,according to certain embodiments.

FIG. 19 illustrates a flow diagram of a process for forming a stacked 3Dstructure integrating a reconstituted substrate by build-up stacking,according to embodiments described herein.

FIGS. 20A-20F schematically illustrate cross-sectional views of astacked 3D structure at different stages of build-up stacking, asdepicted in FIG. 19.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

The present disclosure relates to thin-form-factor reconstitutedsubstrates and methods for forming the same. The reconstitutedsubstrates described herein may be utilized to fabricate homogeneous orheterogeneous high-density 3D integrated devices. In one embodiment, asilicon substrate is structured by laser ablation to include one or morecavities and one or more vias. One or more semiconductor dies of thesame or different types may be placed within the cavities and thereafterembedded in the substrate upon formation of an insulating layer thereon.One or more conductive interconnections are formed in the vias and mayhave contact points redistributed to desired surfaces of thereconstituted substrate. The reconstituted substrate may thereafter beintegrated into a stacked 3D device, such as a 3D DRAM stack.

FIG. 1 illustrates a flow diagram of a representative method 100 offorming a reconstituted substrate and/or subsequent package, which maybe homogeneous or heterogeneous. The method 100 has multiple operations110, 120, 130, and 140 a-140 c. Each operation is described in greaterdetail with reference to FIGS. 2-14D. The method may include one or moreadditional operations which are carried out before any of the definedoperations, between two of the defined operations, or after all of thedefined operations (except where the context excludes the possibility).

In general, the method 100 includes structuring a substrate to be usedas a frame at operation 110, further described in greater detail withreference to FIGS. 2, 3A-3E, and 4A-4B. At operation 120, anintermediary die assembly having one or more embedded dies andinsulating layers is formed, which is described in greater detail withreference to FIGS. 5 and 6A-6K and FIGS. 7 and 8A-8G. One or moreinterconnections are formed in and/or through the intermediary dieassembly to form a functional reconstituted substrate at operation 130,which is described in greater detail with reference to FIGS. 9 and10A-10K. At operation 140, the reconstituted substrate may then have oneor more redistribution layers formed thereon (140 a), be singulated intoindividual packages or systems-in-packages (“SiPs”) (140 b), and/or beutilized to form a stacked 3D structure (140 c). Formation of theredistribution layers is described with reference to FIGS. 11 and12A-12N. Stacking is described with reference to FIGS. 13 and 14A-20F.

FIG. 2 illustrates a flow diagram of a representative method 200 forstructuring a substrate to be utilized as a reconstituted substrateframe. FIGS. 3A-3E schematically illustrate cross-sectional views of asubstrate 302 at different stages of the substrate structuring process200 represented in FIG. 2. Therefore, FIG. 2 and FIGS. 3A-3E are hereindescribed together for clarity.

The method 200 begins at operation 210 and corresponding FIG. 3A,wherein the substrate 302 is exposed to a first defect removal process.The substrate 302 is formed of any suitable substrate material includingbut not limited to a III-V compound semiconductor material, silicon(e.g., having a resistivity between about 1 and about 10 Ohm-com orconductivity of about 100 W/mK), crystalline silicon (e.g., Si<100> orSi<111>), silicon oxide, silicon germanium, doped or undoped silicon,undoped high resistivity silicon (e.g., float zone silicon having lowerdissolved oxygen content and a resistivity between about 5000 and about10000 ohm-cm), doped or undoped polysilicon, silicon nitride, siliconcarbide (e.g., having a conductivity of about 500 W/mK), quartz, glass(e.g., borosilicate glass), sapphire, alumina, and/or ceramic materials.In one embodiment, the substrate 302 is a monocrystalline p-type orn-type silicon substrate. In one embodiment, the substrate 302 is apolycrystalline p-type or n-type silicon substrate. In anotherembodiment, the substrate 302 is a p-type or n-type silicon solarsubstrate. The substrate 302 may further have a polygonal or circularshape. For example, the substrate 302 may include a substantially squaresilicon substrate having lateral dimensions between about 120 mm andabout 180 mm, such as about 150 mm or between about 156 mm and about 166mm, with or without chamfered edges. In another example, the substrate302 may include a circular silicon-containing wafer having a diameterbetween about 20 mm and about 700 mm, such as between about 100 mm andabout 500 mm, for example about 200 mm or about 300 mm.

Unless otherwise noted, embodiments and examples described herein areconducted on substrates having a thickness between about 50 μm and about1500 μm, such as between about 90 μm and about 780 μm. For example, thesubstrate 302 has a thickness between about 100 μm and about 300 μm,such as a thickness between about 110 μm and about 200 μm. In anotherexample, the substrate 302 has a thickness between about 60 μm and about160 μm, such as a thickness between about 80 μm and about 120 μm.

Prior to operation 210, the substrate 302 may be sliced and separatedfrom a bulk material by wire sawing, scribing and breaking, mechanicalabrasive sawing, or laser cutting. Slicing typically causes mechanicaldefects or deformities in substrate surfaces, such as scratches,micro-cracking, chipping, and other mechanical defects. Thus, thesubstrate 302 is exposed to the first defect removal process atoperation 210 to smoothen and planarize surfaces thereof and remove anymechanical defects in preparation for later structuring and packagingoperations. In some embodiments, the substrate 302 may further bethinned by adjusting the process parameters of the first defect removalprocess. For example, a thickness of the substrate 302 may be decreasedwith increased (e.g., additional) exposure to the first defect removalprocess.

In some embodiments, the first defect removal process at operation 210includes exposing the substrate 302 to a substrate polishing processand/or an etch process followed by rinsing and drying processes. Forexample, the substrate 302 may be exposed to a chemical mechanicalpolishing (CMP) process at operation 210. In some embodiments, the etchprocess is a wet etch process, including a buffered etch process that isselective for the removal of desired materials (e.g., contaminants andother undesirable compounds). In other embodiments, the etch process isa wet etch process utilizing an isotropic aqueous etch process. Anysuitable wet etchant or combination of wet etchants may be used for thewet etch process. In one embodiment, the substrate 302 is immersed in anaqueous HF etching solution for etching. In another embodiment, thesubstrate 302 is immersed in an aqueous KOH etching solution foretching. During the etch process, the etching solution may be heated toa temperature between about 30° C. and about 100° C., such as betweenabout 40° C. and about 90° C., in order to accelerate the etchingprocess. For example, the etching solution is heated to a temperature ofabout 70° C. during the etch process. In still other embodiments, theetch process at operation 210 is a dry etch process. An example of a dryetch process includes a plasma-based dry etch process.

The thickness of the substrate 302 may be modulated by controlling thetime of exposure of the substrate 302 to the polishing process and/orthe etchants (e.g., the etching solution) used during the etch process.For example, a final thickness of the substrate 302 may be reduced withincreased exposure to the polishing process and/or etchants.Alternatively, the substrate 302 may have a greater final thickness withdecreased exposure to the polishing process and/or the etchants.

At operations 220 and 230, the now planarized and substantiallydefect-free substrate 302 has one or more features, such as vias 303 andcavities 305, patterned therein and smoothened (two cavities 305 andeight vias 303 are depicted in the lower cross-section of the substrate302 in FIG. 3B for clarity). The vias 303 are utilized to form directcontact electrical interconnections through the substrate 302 and thecavities 305 are utilized to receive and enclose (i.e., embed) one ormore semiconductor dies or devices therein.

In embodiments where the substrate 302 has a relatively small thickness,such as a thickness less than 200 μm, the substrate 302 may be coupledto a carrier plate (not shown) prior to patterning. For example, wherethe substrate 302 has a thickness less than about 100 μm, such as athickness of about 50 μm, the substrate 302 is placed on a carrier platefor mechanical support and stabilization during the substratestructuring processes at operations 220 and 230, thus preventing thesubstrate 302 from breaking. The carrier plate is formed of any suitablechemically and thermally stable rigid material including but not limitedto glass, ceramic, metal, or the like, and has a thickness between about1 mm and about 10 mm. In some embodiments, the carrier plate has atextured surface to hold the substrate 302 in place during structuring.In other embodiments, the carrier plate has a polished or smoothsurface.

The substrate 302 may be coupled to the carrier plate via an adhesivesuch as wax, glue, or any suitable temporary bonding material which maybe applied to the carrier plate by mechanical rolling, pressing,lamination, spin coating, or doctor-blading. In some embodiments, thesubstrate 302 is coupled to the carrier plate via a water-soluble orsolvent-soluble adhesive. In other embodiments, the adhesive is athermal release or UV release adhesive. For example, the substrate 302may be released from the carrier plate by exposure to a bake processwith temperatures between about 50° C. and about 300° C., such astemperatures between about 100° C. and about 200° C., such astemperatures between about 125° C. and about 175° C.

In one embodiment, a desired pattern is formed in the substrate 302,such as a solar substrate or even a semiconductor wafer, by laserablation. The laser ablation system utilized to laser drill features inthe substrate 302 may include any suitable type of laser source. In someexamples, the laser source is an infrared (IR) laser. In some examplesthe laser source is a picosecond UV laser. In other examples, the lasersource is a femtosecond UV laser. In yet other examples, the lasersource is a femtosecond green laser. The laser source generates acontinuous or pulsed laser beam for patterning of the substrate. Forexample, the laser source may generate a pulsed laser beam having afrequency between 5 kHz and 500 kHz, such as between 10 kHz and about200 kHz. In one example, the laser source is configured to deliver apulsed laser beam at a wavelength of between about 200 nm and about 1200nm and at a pulse duration between about 10 ns and about 5000 ns with anoutput power of between about 10 Watts and about 100 Watts. The lasersource is configured to form any desired pattern and features in thesubstrate 302, including the cavities 305 and the vias 303 describedabove and depicted in FIG. 3B.

Similar to the process of separating the substrate 302 from the bulkmaterial, the laser patterning of the substrate 302 may cause unwantedmechanical defects on the surfaces of the substrate 302, such aschipping and cracking. Thus, after forming desired features in thesubstrate 302 by direct laser patterning, the substrate 302 is exposedto a second defect removal and cleaning process at operation 230substantially similar to the first defect removal process describedabove. FIGS. 3B and 3C illustrate the structured substrate 302 beforeand after performing the second damage removal and cleaning process atoperation 230, resulting in a smoothened substrate 302 having thecavities 305 and vias 303 formed therein.

During the second damage removal process, the substrate 302 is etched,rinsed, and dried. The etch process proceeds for a predeterminedduration to smoothen the surfaces of the substrate 302, and inparticular, the surfaces exposed to laser patterning. In another aspect,the etch process is utilized to remove any undesired debris remainingfrom the laser ablation process. The etch process may be isotropic oranisotropic. In some embodiments, the etch process is a wet etch processutilizing any suitable wet etchant or combination of wet etchants inaqueous solution. For example, the substrate 302 may be immersed in anaqueous HF etching solution or an aqueous KOH etching solution. In someembodiments, the etching solution is heated to further accelerate theetching process. For example, the etching solution may be heated to atemperature between about 40° C. and about 80° C., such as between about50° C. and about 70° C., such as a temperature of about 60° C. duringetching of the substrate 302. In still other embodiments, the etchprocess at operation 230 is a dry etch process. An example of a dry etchprocess includes a plasma-based dry etch process.

FIG. 3C illustrates a longitudinal cross-section of the substrate 302after completion of operations 210-230. The substrate 302 is depictedhaving two cavities 305 formed therethrough, each cavity 305 surroundedon either side by two vias 303. Furthermore, the two cavities 305 areshown having different lateral dimensions D₁ and D₂, thus enablingplacement of different types of semiconductor devices and/or dies ineach cavity during subsequent packaging operations. Accordingly, thecavities 305 may be shaped and sized to accommodate any desired devicesand/or dies in any desired arrangement for 2D heterogeneous packagingintegration. Although only two cavities and eight vias are depicted inFIGS. 3B-3E, any number and arrangement of cavities and vias may beformed in the substrate while performing the method 200. Top views ofadditional exemplary arrangements are later described with reference toFIGS. 4A and 4B.

At operation 240, the substrate 302 is then exposed to an optionaloxidation or metallization process to grow an oxide layer 314 or a metalcladding layer 315 on desired surfaces thereof after removal ofmechanical defects. For example, the oxide layer 314 or metal claddinglayer 315 may be formed on all surfaces of the substrate 302 (e.g.,including sidewalls of the cavities 305 and vias 303) such that thelayer 314 or 315 surrounds the substrate 302.

As shown in FIG. 3D, the oxide layer 314 acts as a passivating layer onthe substrate 302 and provides a protective outer barrier againstcorrosion and other forms of damage. In one embodiment, the substrate302 is exposed to a thermal oxidation process to grow the oxide layer314 thereon. The thermal oxidation process is performed at a temperatureof between about 800° C. and about 1200° C., such as between about 850°C. and about 1150° C. For example, the thermal oxidation process isperformed at a temperature of between about 900° C. and about 1100° C.,such as a temperature of between about 950° C. and about 1050° C. In oneembodiment, the thermal oxidation process is a wet oxidation processutilizing water vapor as an oxidant. In one embodiment, the thermaloxidation process is a dry process utilizing molecular oxygen as theoxidant. It is contemplated that the substrate 302 may be exposed to anysuitable oxidation process at operation 240 to form the oxide layer 314thereon. In some embodiments, the oxide layer 314 is a silicon dioxidefilm. The oxide layer 314 formed at operation 240 generally has athickness between about 100 nm and about 3 μm, such as between about 200nm and about 2.5 μm. For example, the oxide layer 314 has a thicknessbetween about 300 nm and about 2 μm, such as about 1.5 μm.

In embodiments where a metal cladding layer 315 is formed on thesubstrate 302 (depicted in FIG. 3E), the metal cladding layer 315 actsas a reference layer (e.g., grounding layer or a voltage supply layer).The metal cladding layer 315 is disposed on the substrate 302 to protectsubsequently integrated semiconductor devices and connections fromelectromagnetic interference and shield semiconductor signals from thesemiconductor material (Si) that is used to form the substrate 302. Inone embodiment, the metal cladding layer 315 includes a conductive metallayer that includes nickel, aluminum, gold, cobalt, silver, palladium,tin, or the like. In one embodiment, the metal cladding layer 315includes a metal layer that includes an alloy or pure metal thatincludes nickel, aluminum, gold, cobalt, silver, palladium, tin, or thelike. The metal cladding layer 315 generally has thickness between about50 nm and about 10 μm such as between about 100 nm and about 5 μm.

The metal cladding layer 315 may be formed by any suitable depositionprocess, including an electroless deposition process, an electroplatingprocess, a chemical vapor deposition process, an evaporation depositionprocess, and/or an atomic layer deposition process. In certainembodiments, at least a portion of the metal cladding layer 315 includesa deposited nickel (Ni) layer formed by direct displacement ordisplacement plating on the surfaces of the substrate 302 (e.g., n-Sisubstrate or p-Si substrate). For example, the substrate 302 is exposedto a nickel displacement plating bath having a composition including 0.5M NiSO₄ and NH₄OH at a temperature between about 60° C. and about 95° C.and a pH of about 11, for a period of between about 2 and about 4minutes. The exposure of the silicon substrate 302 to a nickelion-loaded aqueous electrolyte in the absence of reducing agent causes alocalized oxidation/reduction reaction at the surface of the substrate302, thus leading to plating of metallic nickel thereon. Accordingly,nickel displacement plating enables selective formation of thin and purenickel layers on the silicon material of substrate 302 utilizing stablesolutions. Furthermore, the process is self-limiting and thus, once allsurfaces of the substrate 302 are plated (e.g., there is no remainingsilicon upon which nickel can form), the reaction stops. In certainembodiments, the nickel metal cladding layer 315 may be utilized as aseed layer for plating of additional metal layers, such as for platingof nickel or copper by electroless and/or electrolytic plating methods.In further embodiments, the substrate 302 is exposed to an SC-1pre-cleaning solution and a HF oxide etching solution prior to a nickeldisplacement plating bath to promote adhesion of the nickel metalcladding layer 315 thereto.

FIG. 4A illustrates a schematic top view of an exemplary pattern thatmay be formed in the substrate 302, thus enabling the substrate 302 tobe utilized as a frame during heterogeneous 2D and 3D packagingintegration according to one embodiment. The substrate 302 may bestructured during operations 210-240 as described above with referenceto FIGS. 2 and 3A-3E. As depicted, the substrate 302 is structured toinclude nine identical and quadrilateral regions 412 (separated byscribe lines 410) that may be packaged and singulated into nineindividual 2D heterogeneous packages or SiPs. Although nine identicalregions 412 are shown in FIG. 4A, it is contemplated that any desirednumber of regions and arrangements of features may be structured intothe substrate 302 utilizing the processes described above. In oneexample, the regions 412 are not identical, and include differentfeatures and/or arrangements of features formed therein.

Each region 412 includes five quadrilateral cavities 305 a-305 e, eachcavity 305 a-305 e surrounded by two rows 403 a, 403 b of vias 303 alongmajor sides thereof. As depicted, cavities 305 a-305 c are structured tohave substantially similar morphologies and thus, may each accommodatethe placement (e.g., integration) of the same type of semiconductordevice or die. Cavities 305 d and 305 e, however, have substantiallydiffering morphologies from each other in addition to that of thecavities 305 a-305 c and thus, may accommodate the placement of twoadditional types of semiconductor devices or dies. Accordingly, thestructured substrate 302 may be utilized to form a reconstitutedsubstrate for singulation of heterogonous 2D packages or SiPs havingthree types of semiconductor devices or dies integrated therein.Although depicted as having three types of quadrilateral cavities 305,each region 412 may have more or less than three types of cavities 305with morphologies other than quadrilateral. For example, each region 412may have one type of cavity 305 formed therein, thus enabling theformation of homogeneous 2D packages.

In one embodiment, the cavities 305 and vias 303 have a depth equal tothe thickness of the substrate 302, thus forming holes on opposingsurfaces of the substrate 302 (e.g., through the thickness of thesubstrate 302). For example, the cavities 305 and the vias 303 formed inthe substrate 302 may have a depth of between about 50 μm and about 1mm, such as between about 100 μm and about 200 μm, such as between about110 μm and about 190 μm, depending on the thickness of the substrate302. In other embodiments, the cavities 305 and/or the vias 303 may havea depth equal to or less than the thickness of the substrate 302, thusforming a hole in only one surface (e.g., side) of the substrate 302.

In one embodiment, each cavity 305 has lateral dimensions rangingbetween about 0.5 mm and about 50 mm, such as between about 3 mm andabout 12 mm, such as between about 8 mm and about 11 mm, depending onthe size and number of semiconductor devices or dies to be embeddedtherein during package or reconstituted substrate fabrication.Semiconductor dies generally include a plurality of integratedelectronic circuits that are formed on and/or within a substratematerial, such as a piece of semiconductor material. In one embodiment,the cavities 305 are sized to have lateral dimensions substantiallysimilar to that of the semiconductor devices or dies to be embedded(e.g., integrated) therein. For example, each cavity 305 is formedhaving lateral dimensions (i.e., X-direction or Y-direction in FIG. 4A)exceeding those of the semiconductor devices or dies by less than about150 μm, such as less than about 120 μm, such as less than 100 μm. Havinga reduced variance in the size of the cavities 305 and the semiconductordevices or dies to be embedded therein reduces the amount of gap-fillmaterial necessitated thereafter.

Although each cavity 305 is depicted as being surrounded by two rows 403a, 403 b of vias 303 along major sides thereof, each region 412 may havedifferent arrangements of vias 303. For example, the cavities 305 may besurrounded by more or less than two rows 403 of vias 303 wherein thevias 303 in each row 403 are staggered and unaligned with vias 303 of anadjacent row 403. In some embodiments, the vias 303 are formed assingular and isolated vias through the substrate 302.

Generally, the vias 303 are substantially cylindrical in shape. However,other morphologies for the vias 303 are also contemplated. For example,the vias 303 may have a tapered or conical morphology, wherein adiameter at a first end thereof (e.g., at one surface of the substrate302) is larger than a diameter at a second end thereof. Formation oftapered or conical morphologies may be accomplished by moving the laserbeam of the laser source utilized during structuring in a spiraling(e.g., circular, corkscrew) motion relative to the central axis of eachof the vias 303. The laser beam may also be angled using a motion systemto form tapered vias 303. The same methods may also be utilized to formcylindrical vias 303 having uniform diameters therethrough.

In one embodiment, each via 303 has a diameter ranging between about 20μm and about 200 μm, such as between about 50 μm and about 150 μm, suchas between about 60 μm and about 130 μm, such as between about 80 μm and110 μm. A minimum pitch between centers of the vias 303 is between about70 μm and about 200 μm, such as between about 85 μm and about 160 μm,such as between about 100 μm and 140 μm. Although embodiments aredescribed with reference to FIG. 4A, the substrate structuring processesdescribed above with reference to operations 210-240 and FIGS. 2 and3A-3E may be utilized to form patterned features in the substrate 302having any desired depth, lateral dimensions, and morphologies.

FIG. 4B illustrates a schematic top view of the region 412 with anotherexemplary pattern that may be formed in the substrate 302. In certainembodiments, it may be desirable to place two or more semiconductor diesof the same or different types in a single cavity 305 during packaging,with each semiconductor die having the same or different dimensionsand/or shapes. Accordingly, in some examples, a cavity 305 may have anirregular or asymmetrical shape to accommodate semiconductor dies havingdifferent dimensions and/or shapes. As depicted in FIG. 4B, the region412 includes four quadrilateral and symmetrical cavities 305 a-d and asingle asymmetrical cavity 305 f. The cavity 305 f is shaped toaccommodate two semiconductor dies 326 a and 326 b (shown in phantom)having different dimensions. Although only one asymmetrical cavity 305 fis depicted for accommodating two semiconductor dies 326 a and 326 b inFIG. 4B, it is contemplated that each region 412 may include more orless than one asymmetrical cavity 305 for accommodating any desirednumber of side-by-side dies having any suitable dimensions and shapes.

After structuring, the substrate 302 may be utilized as a frame to forma reconstituted substrate in subsequent packaging operations. FIGS. 5and 7 illustrate flow diagrams of representative methods 500 and 700,respectively, for fabricating an intermediary die assembly 602 aroundthe substrate 302 prior to completed (e.g., final) reconstitutedsubstrate formation. FIGS. 6A-6K schematically illustratecross-sectional views of the substrate 302 at different stages of themethod 500 depicted in FIG. 5, and are herein described together withFIG. 5 for clarity. Similarly, FIGS. 8A-8G schematically illustratecross-sectional views of the substrate 302 at different stages of themethod 700 depicted in FIG. 7, and are herein described together withFIG. 7.

Generally, the method 500 begins at operation 502 and FIG. 6A, wherein afirst side 675 (e.g., a first major surface 606) of the substrate 302,now having desired features formed therein, is placed on a firstinsulating film 616 a. In one embodiment, the first insulating film 616a includes one or more layers 618 a formed of flowable and polymer-baseddielectric materials, such as an insulating build-up material. In theembodiment depicted in FIG. 6A, the first insulating film 616 a includesa flowable layer 618 a formed of an epoxy resin. For example, theflowable layer 618 a may be formed of a ceramic-filler-containing epoxyresin, such as an epoxy resin filled with (e.g., containing)substantially spherical silica (SiO₂) particles. As used herein, theterm “spherical” refers to any round, ellipsoid, or spheroid shape. Forexample, in some embodiments, the ceramic fillers may have an ellipticshape, an oblong oval shape, or other similar round shape. However,other morphologies are also contemplated. Other examples of ceramicfillers that may be utilized to form the flowable layer 618 a and otherlayers of the insulating film 616 a include aluminum nitride (AlN),aluminum oxide (Al₂O₃), silicon carbide (SiC), silicon nitride (Si₃N₄),Sr₂Ce₂Ti₅O₁₆ ceramics, zirconium silicate (ZrSiO₄), wollastonite(CaSiO₃), beryllium oxide (BeO), cerium dioxide (CeO₂), boron nitride(BN), calcium copper titanium oxide (CaCu₃Ti₄O₁₂), magnesium oxide(MgO), titanium dioxide (TiO₂), zinc oxide (ZnO) and the like.

In some examples, the ceramic fillers utilized to form the flowablelayer 618 a have particles ranging in size between about 40 nm and about1.5 μm, such as between about 80 nm and about 1 μm. For example, theceramic fillers utilized to form the flowable layer 618 a have particlesranging in size between about 200 nm and about 800 nm, such as betweenabout 300 nm and about 600 nm. In some embodiments, the ceramic fillersinclude particles having a size less than about 25% of a width ordiameter of the features (e.g., via, cavity, or through-assembly via)formed in the substrate, such as less than about 15% of a desiredfeature's width or diameter.

The flowable layer 618 a typically has a thickness less than about 60μm, such as between about 5 μm and about 50 μm. For example, theflowable layer 618 a has a thickness between about 10 μm and about 25μm. In one embodiment, the insulating film 616 a may further include oneor more protective layers. For example, the insulating film 616 aincludes a polyethylene terephthalate (PET) protective layer 622 a.However, any suitable combination of layers and insulating materials iscontemplated for the insulating film 616 a. In some embodiments, theentire insulating film 616 a has a thickness less than about 120 μm,such as a thickness less than about 90 μm.

The substrate 302, which is coupled to the insulating film 616 a on thefirst side 675 thereof, and specifically to the flowable layer 618 a ofthe insulating film 616 a, may further be optionally placed on a carrier624 for mechanical support during later processing operations. Thecarrier 624 is formed of any suitable mechanically and thermally stablematerial. For example, the carrier 624 is formed ofpolytetrafluoroethylene (PTFE). In another example, the carrier 624 isformed of PET.

At operation 504 and depicted in FIG. 6B, one or more semiconductor dies626 are placed within the cavities 305 formed in the substrate 302 sothat the semiconductor dies 626 are now bound by the insulating film 616a on one side (two semiconductor dies 626 are depicted in FIG. 6B). Inone embodiment, the semiconductor dies 626 are multipurpose dies havingintegrated circuits formed on active surfaces 628 thereof. In oneembodiment, the semiconductor dies 626 are the same type ofsemiconductor devices or dies. In another embodiment, the semiconductordies 626 are different types of semiconductor devices or dies. Thesemiconductor dies 626 are placed within the cavities 305 (e.g.,cavities 350 a-305 e of FIG. 4) and positioned onto a surface of theinsulating film 616 a exposed through the cavities 305. In oneembodiment, the semiconductor dies 626 are placed on an optionaladhesive layer (not shown) disposed or formed on the insulating film 616a.

After placement of the dies 626 within the cavities 305, a firstprotective film 660 is placed over a second side 677 (e.g., surface 608)of the substrate 302 at operation 506 and FIG. 6C. The protective film660 is coupled to the second side 677 of the substrate 302 and oppositeof the first insulating film 616 a such that it contacts and covers theactive surfaces 628 of the dies 626 disposed within the cavities 305. Inone embodiment, the protective film 660 is formed of a similar materialto that of the protective layer 622 a. For example, the protective film660 is formed of PET, such as biaxial PET. However, the protective film660 may be formed of any suitable protective materials. In someembodiments, the protective film 660 has a thickness between about 50 μmand about 150 μm.

The substrate 302, now affixed to the insulating film 616 a on the firstside 675 and the protective film 660 on the second side 677 and furtherhaving dies 626 disposed therein, is exposed to a first laminationprocess at operation 508. During the lamination process, the substrate302 is exposed to elevated temperatures, causing the flowable layer 618a of the insulating film 616 a to soften and flow into open voids orvolumes between the insulating film 616 a and the protective film 660,such as into voids 650 within the vias 303 and gaps 651 between theinterior walls of the cavities 305 and the dies 626. Accordingly, thesemiconductor dies 626 become at least partially embedded within thematerial of the insulating film 616 a and the substrate 302, as depictedin FIG. 6D.

In one embodiment, the lamination process is a vacuum lamination processthat may be performed in an autoclave or other suitable device. In oneembodiment, the lamination process is performed by use of a hot pressingprocess. In one embodiment, the lamination process is performed at atemperature of between about 80° C. and about 140° C. and for a periodbetween about 5 seconds and about 1.5 minutes, such as between about 30seconds and about 1 minute. In some embodiments, the lamination processincludes the application of a pressure of between about 1 psig and about50 psig while a temperature of between about 80° C. and about 140° C. isapplied to substrate 302 and insulating film 616 a for a period betweenabout 5 seconds and about 1.5 minutes. For example, the laminationprocess is performed at a pressure of between about 5 psig and about 40psig and a temperature of between about 100° C. and about 120° C. for aperiod between about 10 seconds and about 1 minute. For example, thelamination process is performed at a temperature of about 110° C. for aperiod of about 20 seconds.

At operation 510, the protective film 660 is removed and the substrate302, now having the laminated insulating material of the flowable layer618 a at least partially surrounding the substrate 302 and the one ormore dies 626, is coupled to a second protective film 662. As depictedin FIG. 6E, the second protective film 662 is coupled to the first side675 of the substrate 302 such that the second protective film 662 isdisposed against (e.g., adjacent) the protective layer 622 a of theinsulating film 616 a. In some embodiments, the substrate 302 nowcoupled to the protective film 662, may be optionally placed on thecarrier 624 for additional mechanical support on the first side 675. Insome embodiments, the protective film 662 is placed on the carrier 624prior to coupling the protective film 662 with the substrate 302, nowlaminated with the insulating film 616 a. Generally, the protective film662 is substantially similar in composition to the protective film 660.For example, the protective film 662 may be formed of PET, such asbiaxial PET. However, the protective film 662 may be formed of anysuitable protective materials. In some embodiments, the protective film662 has a thickness between about 50 μm and about 150 μm.

Upon coupling the substrate 302 to the second protective film 662, asecond insulating film 616 b substantially similar to the firstinsulating film 616 a is placed on the second side 677 of the substrate302 at operation 512 and FIG. 6F, thus replacing the protective film660. In one embodiment, the second insulating film 616 b is positionedon the second side 677 of the substrate 302 such that a flowable layer618 b of the second insulating film 616 b contacts and covers the activesurface 628 of the dies 626 within the cavities 305. In one embodiment,the placement of the second insulating film 616 b on the substrate 302may form one or more voids 650 and gaps 651 between the insulating film616 b and the already-laminated insulating material of the flowablelayer 618 a partially surrounding the one or more dies 626. The secondinsulating film 616 b may include one or more layers formed ofpolymer-based dielectric materials. As depicted in FIG. 6F, the secondinsulating film 616 b includes a flowable layer 618 b, which is similarto the flowable layer 618 a described above. The second insulating film616 b may further include a protective layer 622 b formed of similarmaterials to the protective layer 622 a, such as PET.

At operation 514, a third protective film 664 is placed over the secondinsulating film 616 b, as depicted in FIG. 6G. Generally, the protectivefilm 664 is substantially similar in composition to the protective films660, 662. For example, the protective film 664 is formed of PET, such asbiaxial PET. However, the protective film 664 may be formed of anysuitable protective materials. In some embodiments, the protective film664 has a thickness between about 50 μm and about 150 μm.

The substrate 302, now affixed to the insulating film 616 b andprotective layer 664 on the second side 677 and the protective film 662and optional carrier 624 on the first side 675, is exposed to a secondlamination process at operation 516 and FIG. 6H. Similar to thelamination process at operation 508, the substrate 302 is exposed toelevated temperatures, causing the flowable layer 618 b of theinsulating film 616 b to soften and flow into the voids 650 and gaps 651between the insulating film 616 b and the already-laminated insulatingmaterial of the flowable layer 618 a, thus integrating itself with theinsulating material of the flowable layer 618 a. Accordingly, thecavities 305 and the vias 303 become filled (e.g., packed, sealed) withan insulating material, and the semiconductor dies 626 previously placedwithin the cavities 305 become entirely embedded within the insulatingmaterial of the flowable layers 618 a, 618 b.

In one embodiment, the lamination process is a vacuum lamination processthat may be performed in an autoclave or other suitable device. In oneembodiment, the lamination process is performed by use of a hot pressingprocess. In one embodiment, the lamination process is performed at atemperature of between about 80° C. and about 140° C. and for a periodbetween about 1 minute and about 30 minutes. In some embodiments, thelamination process includes the application of a pressure of betweenabout 10 psig and about 150 psig while a temperature of between about80° C. and about 140° C. is applied to substrate 302 and insulting film616 b for a period between about 1 minute and about 30 minutes. Forexample, the lamination process is performed at a pressure of betweenabout 20 psig and about 100 psig, a temperature of between about 100° C.and about 120° C. for a period between about 2 minutes and 10 minutes.For example, the lamination process is performed at a temperature ofabout 110° C. for a period of about 5 minutes.

After lamination, the substrate 302 is disengaged from the carrier 624and the protective films 662, 664 are removed at operation 518,resulting in a laminated intermediary die assembly 602. As depicted inFIG. 6I, the intermediary die assembly 602 includes the substrate 302having one or more cavities 305 and/or vias 303 formed therein andfilled with the insulating dielectric material of the flowable layers618 a, 618 b, in addition to the dies 626 embedded within the cavities305. The insulating dielectric material of the flowable layers 618 a,618 b encases the substrate 302 such that the insulating material coversat least two surfaces or sides of the substrate 302, such as majorsurfaces 606, 608, and covers all sides of the embedded semiconductordies 626. In some examples, the protective layers 622 a, 622 b are alsoremoved from the intermediary die assembly 602 at operation 518.Generally, the protective layers 622 a and 622 b, the carrier 624, andthe protective films 662 and 664 are removed from the intermediary dieassembly 602 by any suitable mechanical processes, such as peelingtherefrom.

Upon removal of the protective layers 622 a, 622 b and the protectivefilms 662, 664, the intermediary die assembly 602 is exposed to a cureprocess to fully cure (i.e., harden through chemical reactions andcross-linking) the insulating dielectric material of the flowable layers618 a, 618 b, thus forming a cured insulating layer 619. The insulatinglayer 619 substantially surrounds the substrate 302 and thesemiconductor dies 626 embedded therein. For example, the insulatinglayer 619 contacts or encapsulates at least the sides 675, 677 of thesubstrate 302 (including surfaces 606, 608), and at least six sides orsurfaces of each semiconductor die 626, which have rectangular prismshapes as illustrated in FIG. 6I.

In one embodiment, the cure process is performed at high temperatures tofully cure the insulating layer 619. For example, the cure process isperformed at a temperature of between about 140° C. and about 220° C.and for a period between about 15 minutes and about 45 minutes, such asa temperature of between about 160° C. and about 200° C. and for aperiod between about 25 minutes and about 35 minutes. For example, thecure process is performed at a temperature of about 180° C. for a periodof about 30 minutes. In further embodiments, the cure process atoperation 518 is performed at or near ambient (e.g., atmospheric)pressure conditions.

After curing, one or more through-assembly vias 603 are drilled throughthe intermediary die assembly 602 at operation 520, forming channelsthrough the entire thickness of the intermediary die assembly 602 forsubsequent interconnection formation. In some embodiments, theintermediary die assembly 602 may be placed on a carrier, such as thecarrier 624, for mechanical support during the formation of thethrough-assembly vias 603 and subsequent contact holes 632. Thethrough-assembly vias 603 are drilled through the vias 303 that wereformed in the substrate 302 and subsequently filled with the insulatinglayer 619. Thus, the through-assembly vias 603 may be circumferentiallysurrounded by the insulating layer 619 filled within the vias 303. Byhaving the polymer-based dielectric material of the insulating layer 619(e.g., a ceramic-filler-containing epoxy resin material) line the wallsof the vias 303, capacitive coupling between the conductivesilicon-based substrate 302 and interconnections 1044 (described withreference to FIG. 9 and FIGS. 10E-10K), and thus capacitive couplingbetween adjacently positioned vias 303 and/or redistribution connections1244 (described with reference to FIG. 11 and FIGS. 12H-12N), in acompleted 2D reconstituted substrate 1000 is significantly reduced ascompared to other conventional interconnecting structures that utilizeconventional via insulating liners or films. Furthermore, the flowablenature of the epoxy resin material enables more consistent and reliableencapsulation and insulation, thus enhancing electrical performance byminimizing leakage current of the completed reconstituted substrate1000.

In one embodiment, the through-assembly vias 603 have a diameter of lessthan about 100 μm, such as less than about 75 μm. For example, thethrough-assembly vias 603 have a diameter of less than about 60 μm, suchas less than about 50 μm. In one embodiment, the through-assembly vias603 have a diameter of between about 25 μm and about 50 μm, such as adiameter of between about 35 μm and about 40 μm. In one embodiment, thethrough assembly vias 603 are formed using any suitable mechanicalprocess. For example, the through-assembly vias 603 are formed using amechanical drilling process. In one embodiment, through-assembly vias603 are formed through the intermediary die assembly 602 by laserablation. For example, the through-assembly vias 603 are formed using anultraviolet laser. In one embodiment, the laser source utilized forlaser ablation has a frequency between about 5 kHz and about 500 kHz. Inone embodiment, the laser source is configured to deliver a pulsed laserbeam at a pulse duration between about 10 ns and about 100 ns with apulse energy of between about 50 microjoules (μJ) and about 500 μJ.Utilizing an epoxy resin material having small ceramic filler particlesfor the insulating layer 619 promotes more precise and accurate laserpatterning of small-diameter vias, such as the vias 603, as the smallceramic filler particles therein exhibit reduced laser light reflection,scattering, diffraction, and transmission of the laser light away fromthe area in which the via is to be formed during the laser ablationprocess.

At operation 522 and FIG. 6K, one or more contact holes 632 are drilledthrough the insulating layer 619 to expose one or more contacts 630formed on the active surface 628 of each embedded semiconductor die 626.The contact holes 632 are drilled through the insulating layer 619 bylaser ablation, leaving all external surfaces of the semiconductor dies626 covered and surrounded by the insulating layer 619 and the contacts630 exposed. Thus, the contacts 630 are exposed by the formation of thecontact holes 632. In one embodiment, the laser source may generate apulsed laser beam having a frequency between about 100 kHz and about1000 kHz. In one embodiment, the laser source is configured to deliver apulsed laser beam at a wavelength of between about 100 nm and about 2000nm, at a pulse duration between about 10E-4 ns and about 10E-2 ns, andwith a pulse energy of between about 10 μJ and about 300 μJ. In oneembodiment, the contact holes 632 are drilled using a CO₂, green, or UVlaser. In one embodiment, the contact holes 632 have a diameter ofbetween about 5 μm and about 60 μm, such as a diameter of between about20 μm and about 50 μm.

After the formation of the contact holes 632, the intermediary dieassembly 602 is exposed to a de-smear process at operation 522 to removeany unwanted residues and/or debris caused by laser ablation during theformation of the through-assembly vias 603 and the contact holes 632.The de-smear process thus cleans the through-assembly vias 603 andcontact holes 632 and fully exposes the contacts 630 on the activesurfaces 628 of the embedded semiconductor die 626 for subsequentmetallization. In one embodiment, the de-smear process is a wet de-smearprocess. Any suitable aqueous etchants, solvents, and/or combinationsthereof may be utilized for the wet de-smear process. In one example, apotassium permanganate (KMnO₄) solution may be utilized as an etchant.Depending on the residue thickness, exposure of the intermediary dieassembly 602 to the wet de-smear process at operation 522 may be varied.In another embodiment, the de-smear process is a dry de-smear process.For example, the de-smear process may be a plasma de-smear process withan O₂:CF₄ mixture gas. The plasma de-smear process may includegenerating a plasma by applying a power of about 700 W and flowingO₂:CF₄ at a ratio of about 10:1 (e.g., 100:10 sccm) for a time periodbetween about 60 seconds and about 120 seconds. In further embodiments,the de-smear process is a combination of wet and dry processes.

Following the de-smear process at operation 522, the intermediary dieassembly 602 is ready for the formation of interconnection pathstherein, described below with reference to FIG. 9 and FIGS. 10A-10K.

As previously discussed, FIG. 5 and FIGS. 6A-6K illustrate arepresentative method 500 for forming the intermediary die assembly 602.FIG. 7 and FIGS. 8A-8G illustrate an alternative method 700substantially similar to the method 500 but with fewer operations. Themethod 700 generally includes seven operations 710-770. However,operations 710, 720, 760, and 770 of the method 700 are substantiallysimilar to the operations 502, 504, 520, and 522 of the method 500,respectively. Thus, only operations 730, 740, and 750, depicted in FIGS.8C, 8D, and 8E, respectively, are herein described for clarity.

Accordingly, after placement of the one or more semiconductor dies 626onto a surface of the insulating film 616 a exposed through the cavities305, the second insulating film 616 b is positioned over the second side677 (e.g., major surface 608) of the substrate 302 at operation 730 andFIG. 8C, prior to lamination. In some embodiments, the second insulatingfilm 616 b is positioned on the second side 677 of the substrate 302such that the flowable layer 618 b of the second insulating film 616 bcontacts and covers the active surface 628 of the semiconductor dies 626within the cavities 305. In some embodiments, a second carrier 825 isaffixed to the protective layer 622 b of the second insulating film 616b for additional mechanical support during later processing operations.As depicted in FIG. 8C, one or more voids 650 are formed between theinsulating films 616 a and 616 b through the vias 303 and gaps 651between the semiconductor dies 626 and interior walls of the cavities305.

At operation 740 and FIG. 8D, the substrate 302, now affixed to theinsulating films 616 a and 616 b and having dies 626 disposed therein,is exposed to a single lamination process. During the single laminationprocess, the substrate 302 is exposed to elevated temperatures, causingthe flowable layers 618 a and 618 b of both insulating films 616 a, 616b to soften and flow into the open voids 650 or gaps 651 between theinsulating films 616 a, 616 b. Accordingly, the semiconductor dies 626become embedded within the material of the insulating films 616 a, 616b, and the vias 303 filled therewith.

Similar to the lamination processes described with reference to FIG. 5and FIGS. 6A-6K, the lamination process at operation 740 may be a vacuumlamination process that may be performed in an autoclave or othersuitable device. In another embodiment, the lamination process isperformed by use of a hot pressing process. In one embodiment, thelamination process is performed at a temperature of between about 80° C.and about 140° C. and for a period between about 1 minute and about 30minutes. In some embodiments, the lamination process includes theapplication of a pressure of between about 1 psig and about 150 psigwhile a temperature of between about 80° C. and about 140° C. is appliedto substrate 302 and insulating film 616 a, 616 b layers for a periodbetween about 1 minute and about 30 minutes. For example, the laminationprocess is performed at a pressure of between about 10 psig and about100 psig, a temperature of between about 100° C. and about 120° C. for aperiod between about 2 minutes and 10 minutes. For example, thelamination process is performed at a temperature of about 110° C. for aperiod of about 5 minutes.

At operation 750, the one or more protective layers of the insulatingfilms 616 a and 616 b are removed from the substrate 302, resulting inthe laminated intermediary die assembly 602. As depicted in FIG. 8E, theintermediary die assembly 602 includes the substrate 302 having one ormore cavities 305 and/or vias 303 formed therein and filled with theinsulating dielectric material of the flowable layers 618 a, 618 b, aswell as the embedded dies 626 within the cavities 305. The insulatingmaterial encases the substrate 302 such that the insulating materialcovers at least two surfaces or sides of the substrate 302, for examplemajor surfaces 606, 608. In one example, the protective layers 622 a,622 b are removed from the intermediary die assembly 602, and thus theintermediary die assembly 602 is disengaged from the carriers 624, 825.Generally, the protective layers 622 a, 622 b and the carriers 624, 825are removed by any suitable mechanical processes, such as peelingtherefrom.

Upon removal of the protective layers 622 a, 622 b, the intermediary dieassembly 602 is exposed to a cure process to fully cure the insulatingdielectric material of the flowable layers 618 a, 618 b. Curing of theinsulating material results in the formation of the cured insulatinglayer 619. As depicted in FIG. 8E and similar to operation 518corresponding with FIG. 71, the insulating layer 619 substantiallysurrounds the substrate 302 and the semiconductor dies 626 embeddedtherein.

In one embodiment, the cure process is performed at high temperatures tofully cure the intermediary die assembly 602. For example, the cureprocess is performed at a temperature of between about 140° C. and about220° C. and for a period between about 15 minutes and about 45 minutes,such as a temperature of between about 160° C. and about 200° C. and fora period between about 25 minutes and about 35 minutes. For example, thecure process is performed at a temperature of about 180° C. for a periodof about 30 minutes. In further embodiments, the cure process atoperation 750 is performed at or near ambient (e.g. atmospheric)pressure conditions.

After curing at operation 750, the method 700 is substantially similarto operations 520 and 522 of the method 500. For example, theintermediary die assembly 602 has one or more through-assembly vias 603and one or more contact holes 632 drilled through the insulating layer619. Subsequently, the intermediary die assembly 602 is exposed to ade-smear process, after which the intermediary die assembly 602 is readyfor the formation of interconnection paths therein, as described below.

FIG. 9 illustrates a flow diagram of a representative method 900 offorming electrical interconnections through the intermediary dieassembly 602. FIGS. 10A-10K schematically illustrate cross-sectionalviews of the intermediary die assembly 602 at different stages of theprocess of the method 900 depicted in FIG. 9. Thus, FIG. 9 and FIGS.10A-10K are herein described together for clarity.

In one embodiment, the electrical interconnections formed through theintermediary die assembly 602 are formed of copper. Thus, the method 900may optionally begin at operation 910 and FIG. 10A wherein theintermediary die assembly 602, having through-assembly vias 603 andcontact holes 632 formed therein, has an adhesion layer 1040 and/or aseed layer 1042 formed thereon. An enlarged partial view of the adhesionlayer 1040 and the seed layer 1042 formed on the intermediary dieassembly 602 is depicted in FIG. 10H for reference. The adhesion layer1040 may be formed on desired surfaces of the insulating layer 619, suchas major surfaces 1005, 1007 of the intermediary die assembly 602, aswell as on the active surfaces 628 within the contact holes 632 on eachsemiconductor die 626 and interior walls of the through-assembly vias603, to assist in promoting adhesion and blocking diffusion of thesubsequently formed seed layer 1042 and copper interconnections 1044.Thus, in one embodiment, the adhesion layer 1040 acts as an adhesionlayer; in another embodiment, the adhesion layer 1040 acts as a barrierlayer. In both embodiments, however, the adhesion layer 1040 will behereinafter described as an “adhesion layer.”

In one embodiment, the optional adhesion layer 1040 is formed oftitanium, titanium nitride, tantalum, tantalum nitride, manganese,manganese oxide, molybdenum, cobalt oxide, cobalt nitride, or any othersuitable materials or combinations thereof. In one embodiment, theadhesion layer 1040 has a thickness of between about 10 nm and about 300nm, such as between about 50 nm and about 150 nm. For example, theadhesion layer 1040 has a thickness between about 75 nm and about 125nm, such as about 100 nm. The adhesion layer 1040 is formed by anysuitable deposition process, including but not limited to chemical vapordeposition (CVD), physical vapor deposition (PVD), plasma enhanced CVD(PECVD), atomic layer deposition (ALD), or the like.

The optional seed layer 1042 may be formed on the adhesion layer 1040 ordirectly on the insulating layer 619 (e.g., without the formation of theadhesion layer 1040). The seed layer 1042 is formed of a conductivematerial such as copper, tungsten, aluminum, silver, gold, or any othersuitable materials or combinations thereof. Where the seed layer 1042and subsequently plated interconnections 1044 are formed of the sameconductive material, the seed layer 1042 and the interconnections 1044may have different grain sizes. For example, the seed layer 1042, whendeposited electrolessly and when composed of copper, typically has agrain size between 20 nm and 100 nm. The electrodeposited copperinterconnection 1044 typically has a larger grain size of the order of100 nm-5 um. When the seed layer 1042 is deposited by sputtering (PVD),then the grain size is also smaller than the electroplated copperinterconnection 1044 formed thereon. In the case of PVD (sputtering),the grain size in the seed layer 1042 is also of the order of 20 nm to100 nm.

In one embodiment, the seed layer 1042 has a thickness between about 50nm and about 500 nm, such as between about 100 nm and about 300 nm. Forexample, the seed layer 1042 has a thickness between about 150 nm andabout 250 nm, such as about 200 nm. In one embodiment, the seed layer1042 has a thickness of between about 0.1 μm and about 1.5 μm. Similarto the adhesion layer 1040, the seed layer 1042 is formed by anysuitable deposition process, such as CVD, PVD, PECVD, ALD dry processes,wet electroless plating processes, or the like. In one embodiment, amolybdenum adhesion layer 1040 is formed on the intermediary dieassembly in combination with a seed layer 1042 formed of copper. TheMo—Cu adhesion and seed layer combination enables improved adhesion withthe surfaces of the insulating layer 619 and reduces undercut ofconductive interconnect lines during a subsequent seed layer etchprocess at operation 970.

At operations 920 and 930, corresponding to FIGS. 10B and 10C,respectively, a spin-on/spray-on or dry resist film 1050, such as aphotoresist, is applied on both major surfaces 1005, 1007 of theintermediary die assembly 602 and is subsequently patterned. In oneembodiment, the resist film 1050 is patterned via selective exposure toUV radiation. In one embodiment, an adhesion promoter (not shown) isapplied to the intermediary die assembly 602 prior to formation of theresist film 1050. The adhesion promoter improves adhesion of the resistfilm 1050 to the intermediary die assembly 602 by producing aninterfacial bonding layer for the resist film 1050 and by removing anymoisture from the surface of the intermediary die assembly 602. In someembodiments, the adhesion promoter is formed of bis(trimethylsilyl)amineor hexamethyldisilazane (HMDS) and propylene glycol monomethyl etheracetate (PGMEA).

At operation 940 and FIG. 10D, the intermediary die assembly 602 isexposed to resist film development, ashing, and descum processes. Incertain embodiments, the descum process is an oxygen plasma treatmentfor removal of any residual organic resist residues. As depicted in FIG.10D, the development of the resist film 1050 results in exposure of thethrough-assembly vias 603 and contact holes 632, now having an adhesionlayer 1040 and a seed layer 1042 formed thereon. In one embodiment, thefilm development process is a wet process, such as a wet process thatincludes exposing the resist to a solvent. In one embodiment, the filmdevelopment process is a wet etch process utilizing an aqueous etchprocess. In other embodiments, the film development process is a wetetch process utilizing a buffered etch process selective for a desiredmaterial. Any suitable wet solvents or combination of wet etchants maybe used for the resist film development process.

At operations 950 and 960, corresponding to FIGS. 10E and 10Frespectively, interconnections 1044 are formed on exposed surfaces ofthe intermediary die assembly 602, such as through the exposedthrough-assembly vias 603 and contact holes 632, and the resist film1050 is thereafter removed. The interconnections 1044 are formed by anysuitable methods including electroplating and electroless deposition. Inone embodiment, the resist film 1050 is removed via a wet process. Asdepicted in FIGS. 10E and 10F, the formed interconnections 1044completely fill the through-assembly vias 603 and contact holes 632 oronly cover inner circumferential walls thereof and protrude from thesurfaces 1005, 1007 of the intermediary die assembly 602 upon removal ofthe resist film 1050. For example, the interconnections 1044 may linethe inner circumferential walls of the through-assembly vias 603 andhave hollow cores. In one embodiment, the interconnections 1044 areformed of copper. In other embodiments, the interconnections 1044 may beformed of any suitable conductive material including but not limited toaluminum, gold, nickel, silver, palladium, tin, or the like.

In some embodiments, the interconnections 1044 include lateral trace(e.g., line or pad) regions for electrical connection ofinterconnections 1044 with other electrical contacts or devices, such asredistribution connections 1244 described below. The lateral traceregions can include a portion of the conductive layer formed inoperation 950 and will typically extend across a portion of the majorsurfaces 1007 or 1005.

At operation 970 and FIG. 10G, the intermediary die assembly 602 havinginterconnections 1044 formed therein is exposed to an adhesion and/orseed layer etch process to remove the adhesion layer 1040 and the seedlayer 1042, thus resulting in the formation of the completedreconstituted substrate 1000. In one embodiment, the seed layer etch isa wet etch process including a rinse and drying of the intermediary dieassembly 602. In one embodiment, the seed layer etch process is abuffered etch process selective for a desired material such as copper,tungsten, aluminum, silver, or gold. In other embodiments, the etchprocess is an aqueous etch process. Any suitable wet etchant orcombination of wet etchants may be used for the seed layer etch process.

FIGS. 10I and 10J depict further exemplary arrangements for thereconstituted substrate 1000 according to certain embodiments. Thepackaging schemes depicted in FIGS. 10I and 10J are particularlybeneficial for memory die stacking, as they reduce the amount ofoperations required to stack a desired number of memory dies (e.g.,stacking eight memory dies to form a “byte” now only requires stackingof four packages or reconstituted substrates).

As shown, the reconstituted substrate 1000 includes two semiconductordies 626 stacked backside-to-backside in a die stack 1026 within eachcavity 305, wherein the backsides of the semiconductor dies 626 arecoupled to one another by an adhesive layer 1048. Accordingly, activesides 628 of the stacked semiconductor dies 626 face opposite sides ofthe reconstituted substrate 1000 and have interconnections 1044extending in opposite directions therefrom. In certain embodiments, thestacked semiconductor dies 626 are of the same type and/or havesubstantially the same lateral dimensions, as shown in FIG. 10I. Incertain other embodiments, the stacked semiconductor dies 626 are ofdifferent types and/or have different lateral dimensions, shown in FIG.10J. In such embodiments, a dummy die 627 may be placed alongside thesemiconductor die 626 having the smaller lateral dimension to ensuresubstantially similar overall dimensions of each layer of the die stack1026. The adhesive layer 1048 utilized to couple the backsides of thesemiconductor dies 626 may be any suitable type of adhesive, such as alaminated adhesive material, die attach film, glue, or the like.

To form the arrangements depicted in FIGS. 10I and 10J, thesemiconductor dies 626 can be attached to each other prior to placementof the die stack 1026 within cavities 305 of the substrate 302. Anexemplary process flow for forming the die stack 1026 is shown in FIG.10K. As depicted, backsides of two die substrates 1002 (e.g., DRAMsubstrates) are aligned and bonded to each other using the adhesivelayer 1048. In certain embodiments, the die substrates 1002 may bethinned before or after bonding, depending on the desired thickness ofthe die stack 1026. The die substrates 1002 are then singulated intoindividual die stacks 1026, which may be placed within cavities 305 ofthe substrate 302 and encapsulated within the insulating layer 619, asdescribed with reference to methods 500 and 700. Thereafter,interconnections and/or redistribution layers may be formed according toany of the operations described herein (e.g., methods 900 and 1200),substantially similar to examples wherein a single semiconductor die 626or side-by-side semiconductor dies 626 are embedded within a cavity 305of the substrate 302.

Following the adhesion and/or seed layer etch process at operation 970,the reconstituted substrate 1000 may be singulated into one or moreelectrically functioning packages or SiPs (e.g., each singulated packageor SiP may include a single region 412 of the substrate 302, now havingthe insulating layer 619 and interconnections 1044 formed thereon, andthe semiconductor dies 626 embedded therein). Each package or SiP maythereafter be integrated with other semiconductor devices and packagesin various 2.5D and 3D arrangements and architectures. For example, thepackages or SiPs may be vertically stacked with additional packages orSiPs and/or other semiconductor devices and systems to form homogeneousor heterogeneous 3D stacked systems. Alternatively, the reconstitutedsubstrate 1000 may be integrated with additional semiconductor devicesand systems prior to singulation. Such 3D integration of the 2Dreconstituted substrate 1000 is further described below with referenceto FIG. 13 and FIGS. 14A-14D.

In yet another embodiment, upon etching of the adhesion and/or seedlayers, the reconstituted substrate 1000 may have one or moreredistribution layers 1258, 1260 (shown in FIGS. 12K-12N) formed thereonas needed to enable rerouting and/or extension of contact points of theinterconnections 1044 to desired locations on the surfaces of thereconstituted substrate 1000. FIG. 11 illustrates a flow diagram of arepresentative method 1100 of forming a redistribution layer 1258 on thereconstituted substrate 1000. FIGS. 12A-12N schematically illustratecross-sectional views of the reconstituted substrate 1000 at differentstages of the method 1100, depicted in FIG. 11. Thus, FIG. 11 and FIGS.12A-12N are herein described together for clarity.

The method 1100 is substantially similar to the methods 500, 700, and900 described above. Generally, the method 1100 begins at operation 1102and FIG. 12A, wherein an insulating film 1216 is placed on thereconstituted substrate 1000, already having the insulating layer 619formed thereon, and thereafter laminated. The insulating film 1216 maybe substantially similar to the insulating films 616 and may include oneor more flowable layers 1218 formed of polymer-based dielectricmaterials and one or more protective layers 1222 formed of PET.

In one embodiment, the flowable layer 1218 includes an epoxy resinmaterial. In one embodiment, the flowable layer 1218 includes aceramic-filler-containing epoxy resin material. In another embodiment,the flowable layer 1218 includes a photodefinable polyimide material.The material properties of photodefinable polyimide enable the formationof smaller (e.g., narrower) vias through the resulting interconnectredistribution layer formed from the insulating film 1216. However, anysuitable combination of flowable layers 1218 and insulating materials iscontemplated for the insulating film 1216. For example, the insulatingfilm 1216 may include one or more flowable layers 1218 including anon-photosensitive polyimide material, a polybenzoxazole (PBO) material,a silicon dioxide material, and/or a silicon nitride material.

In some examples, the material of the flowable layer 1218 is differentfrom the flowable layers 618 of the insulating films 616. For example,the flowable layers 618 may include a ceramic-filler-containing epoxyresin material and the flowable layer 1218 may include a photodefinablepolyimide material. In another example, the flowable layer 1218 includesa different inorganic dielectric material from the flowable layers 618.For example, the flowable layers 618 may include aceramic-filler-containing epoxy resin material and the flowable layer1218 may include a silicon dioxide material.

The insulating film 1216 has a total thickness of less than about 120μm, such as between about 40 μm and about 100 μm. For example, theinsulating film 1216 including the flowable layer 1218 and theprotective layer 1222 has a total thickness of between about 50 μm andabout 90 μm. In one embodiment, the flowable layer 1218 has a thicknessof less than about 60 μm, such as a thickness between about 5 μm andabout 50 μm, such as a thickness of about 20 μm. The insulating film1216 is placed on a surface of the reconstituted substrate 1000 havingexposed interconnections 1044 that are coupled to the contacts 630 onthe active surface 628 of semiconductor dies 626 and/or coupled to themetallized through-assembly vias 603, such as the major surface 1007.

After placement of the insulating film 1216, the reconstituted substrate1000 is exposed to a lamination process substantially similar to thelamination process described with reference to operations 508, 516, and740. The reconstituted substrate 1000 is exposed to elevatedtemperatures to soften the flowable layer 1218, which subsequently bondsto the insulating layer 619 already formed on the reconstitutedsubstrate 1000. Thus, in one embodiment, the flowable layer 1218 becomesintegrated with the insulating layer 619 and forms an extension thereof.The integration of the flowable layer 1218 and the insulating layer 619results in an expanded and integrated insulating layer 619, covering thepreviously exposed interconnections 1044. Accordingly, the bondedflowable layer 1218 and the insulating layer 619 will herein be jointlydescribed as the insulating layer 619. In other embodiments, however,the lamination and subsequent curing of the flowable layer 1218 forms asecond insulating layer (not shown) on the insulating layer 619. In someexamples, the second insulating layer is formed of a different materiallayer than the insulating layer 619.

In one embodiment, the lamination process is a vacuum lamination processthat may be performed in an autoclave or other suitable device. In oneembodiment, the lamination process is performed by use of a hot pressingprocess. In one embodiment, the lamination process is performed at atemperature of between about 80° C. and about 140° C. and for a periodbetween about 1 minute and about 30 minutes. In some embodiments, thelamination process includes the application of a pressure of between 10psig and about 100 psig while a temperature of between about 80° C. andabout 140° C. is applied to the substrate 302 and insulating film 1216for a period between about 1 minute and about 30 minutes. For example,the lamination process is performed at a pressure of between about 30psig and about 80 psig and a temperature of between about 100° C. andabout 120° C. for a period between about 2 minutes and about 10 minutes.For example, the lamination process is performed at a temperature ofabout 110° C. for a period of about 5 minutes. In further examples, thelamination process is performed at a pressure between about 30 psig andabout 70 psig, such as about 50 psig.

At operation 1104 and FIG. 12B, the protective layer 1222 is removedfrom the reconstituted substrate 1000 by mechanical processes. Afterremoval of the protective layer 1322 and carrier 1324, the reconstitutedsubstrate 1000 is exposed to a cure process to fully cure the newlyexpanded insulating layer 619. In one embodiment, the cure process issubstantially similar to the cure process described with reference tooperations 518 and 750. For example, the cure process is performed at atemperature of between about 140° C. and about 220° C. and for a periodbetween about 15 minutes and about 45 minutes, such as a temperature ofbetween about 160° C. and about 200° C. and for a period between about25 minutes and about 35 minutes. For example, the cure process isperformed at a temperature of about 180° C. for a period of about 30minutes. In further embodiments, the cure process at operation 1104 isperformed at or near ambient pressure conditions.

The reconstituted substrate 1000 is then selectively patterned by laserablation at operation 1106 and FIG. 12C. The laser ablation at operation1106 forms redistribution vias 1203 through the newly expandedinsulating layer 619 and exposes desired interconnections 1044 forredistribution of contact points thereof. In one embodiment, theredistribution vias 1203 have a diameter of between about 5 μm and about60 μm, such as a diameter of between about 10 μm and about 50 μm, suchas between about 20 μm and about 45 μm. In one embodiment, the laserablation process at operation 1106 is performed utilizing a CO₂ laser.In one embodiment, the laser ablation process at operation 1106 isperformed utilizing a UV laser. In one embodiment, the laser ablationprocess at operation 1106 is performed utilizing a green laser. Forexample, the laser source may generate a pulsed laser beam having afrequency between about 100 kHz and about 1000 kHz. In one example, thelaser source is configured to deliver a pulsed laser beam at awavelength of between about 100 nm and about 2000 nm, at a pulseduration between about 10E-4 ns and about 10E-2 ns, and with a pulseenergy of between about 10 μJ and about 300 μJ.

Upon patterning of the reconstituted substrate 1000, the reconstitutedsubstrate 1000 is exposed to a de-smear process substantially similar tothe de-smear process at operations 522 and 770. During the de-smearprocess at operation 1106, any unwanted residues and debris formed bylaser ablation during the formation of the redistribution vias 1203 areremoved from the redistribution vias 1203 to clear (e.g., clean) thesurfaces thereof for subsequent metallization. In one embodiment, thede-smear process is a wet process. Any suitable aqueous etchants,solvents, and/or combinations thereof may be utilized for the wetde-smear process. In one example, KMnO₄ solution may be utilized as anetchant. In another embodiment, the de-smear process is a dry de-smearprocess. For example, the de-smear process may be a plasma de-smearprocess with an O₂/CF₄ mixture gas. In further embodiments, the de-smearprocess is a combination of wet and dry processes.

At operation 1108 and FIG. 12D, an optional adhesion layer 1240 and/orseed layer 1242 are formed on the insulating layer 619. In oneembodiment, the adhesion layer 1240 is formed from titanium, titaniumnitride, tantalum, tantalum nitride, manganese, manganese oxide,molybdenum, cobalt oxide, cobalt nitride, or any other suitablematerials or combinations thereof. In one embodiment, the adhesion layer1240 has a thickness of between about 10 nm and about 300 nm, such asbetween about 50 nm and about 150 nm. For example, the adhesion layer1240 has a thickness between about 75 nm and about 125 nm, such as about100 nm. The adhesion layer 1240 may be formed by any suitable depositionprocess, including but not limited to CVD, PVD, PECVD, ALD, or the like.

The optional seed layer 1242 is formed from a conductive material suchas copper, tungsten, aluminum, silver, gold, or any other suitablematerials or combinations thereof. In one embodiment, the seed layer1242 has a thickness between about 50 nm and about 500 nm, such asbetween about 100 nm and about 300 nm. For example, the seed layer 1242has a thickness between about 150 nm and about 250 nm, such as about 200nm. In one embodiment, the seed layer 1242 has a thickness of betweenabout 0.1 μm and about 1.5 μm. Similar to the adhesion layer 1240, theseed layer 1242 may be formed by any suitable deposition process, suchas CVD, PVD, PECVD, ALD dry processes, wet electroless platingprocesses, or the like. In one embodiment, a molybdenum adhesion layer1240 and a copper seed layer 1242 are formed on the reconstitutedsubstrate 1000 to reduce undercut of conductive interconnect linesduring a subsequent seed layer etch process at operation 1120.

At operations 1110, 1112, and 1114, corresponding to FIGS. 12E, 12F, and12G respectively, a spin-on/spray-on or dry resist film 1250, such as aphotoresist, is applied over the adhesion and/or seed surfaces of thereconstituted substrate 1000 and subsequently patterned and developed.In one embodiment, an adhesion promoter (not shown) is applied to thereconstituted substrate 1000 prior to placement of the resist film 1250.The exposure and development of the resist film 1250 results in theopening of the redistribution vias 1203 and exposure of the insulatinglayer 619, adhesion layer 1240, or copper seed layer 1242 for formationof redistribution connections 1244 thereon. Thus, patterning of theresist film 1250 may be performed by selectively exposing portions ofthe resist film 1250 to UV radiation and subsequent development of theresist film 1250 by a wet process, such as a wet etch process. In oneembodiment, the resist film development process is a wet etch processutilizing a buffered etch process selective for a desired material. Inother embodiments, the resist film development process is a wet etchprocess utilizing an aqueous etch process. Any suitable wet etchant orcombination of wet etchants may be used for the resist film developmentprocess.

At operations 1116 and 1118, corresponding to FIGS. 12H and 12Irespectively, redistribution connections 1244 are formed on exposedsurfaces of the reconstituted substrate 1000, such as through theexposed redistribution vias 1203, and the resist film 1250 is thereafterremoved. The redistribution connections 1244 are formed by any suitablemethods, including electroplating and electroless deposition. In oneembodiment, the resist film 1250 is removed via a wet process. Asdepicted in FIGS. 12H and 12I, the redistribution connections 1244 fillthe redistribution vias 1203 and protrude from the surfaces of thereconstituted substrate 1000 upon removal of the resist film 1250. Inone embodiment, the redistribution connections 1244 are formed ofcopper. In other embodiments, the redistribution connections 1244 may beformed of any suitable conductive material including but not limited toaluminum, gold, nickel, silver, palladium, tin, or the like.

As described with reference to the interconnections 1044, theredistribution connections 1244 may also include lateral trace regionsfor electrical connection of redistribution connections 1244 with otherelectrical contacts or devices. The lateral trace regions can include aportion of the conductive layer formed in operation 1116 and willtypically extend across a portion of the major surfaces of thereconstituted substrate 1000.

At operation 1120 and FIG. 12J, the reconstituted substrate 1000 havingthe redistribution connections 1244 formed thereon is exposed to anadhesion and/or seed layer etch process substantially similar to that ofoperation 970. In one embodiment, the adhesion and/or seed layer etch isa wet etch process including a rinse and drying of the reconstitutedsubstrate 1000. In one embodiment, the adhesion and/or seed layer etchprocess is a wet etch process utilizing a buffered etch processselective for a desired material of the seed layer 1242. In otherembodiments, the etch process is a wet etch process utilizing an aqueousetch process. Any suitable wet etchant or combination of wet etchantsmay be used for the seed layer etch process.

At operation 1122 and depicted in FIG. 12K, one or more functional 2Dpackages 1200 may be singulated from the 2D reconstituted substrate1000. (Although described as a package, the packages 1200 may also referto SiPs and other functional packaged devices.) In some embodiments,however, additional redistribution layers may be formed on thereconstituted substrate 1000 prior to singulation of packages 1200 byutilizing the sequences and processes described above. For example, oneor more additional redistribution layers 1260 may be formed on a side orsurface of the reconstituted substrate 1000 opposite of the firstredistribution layer 1258, such as the major surface 1007, as depictedin FIG. 12L. Alternatively, one or more additional redistribution layers1260 may be formed on the same side or surface of the firstredistribution layer 1258, such as major surface 1007. The packages 1200may then be singulated from the reconstituted substrate 1000 after alldesired redistribution layers are formed. Each package 1200 maythereafter be integrated with other semiconductor devices and packagesin desired 2.5D and 3D arrangements and architectures, which may beheterogeneous or homogeneous. For example, the packages 1200 may bevertically stacked with other semiconductor devices and systems to formheterogeneous 3D stacked systems. In yet another embodiment, however,the reconstituted substrate 1000 having one or more redistributionlayers 1258, 1260 formed thereon may be 3D integrated with additionalsemiconductor devices and systems prior to singulation into individual3D packages or SiPs, which may be heterogeneous or homogeneous.

FIGS. 12L-12N further depict packages 1200 wherein the reconstitutedsubstrate 1000 includes the oxide layer 314 or the metal cladding layer315. As shown in FIG. 12L, the oxide layer 314 is formed on all surfacesof the substrate 302, including the sidewalls of the cavities 305 andthe vias 303, which now have semiconductor dies 626 or interconnections1044 disposed therein and surrounded by the insulating layer 619. Theflowable dielectric material of the insulating layer 619 surrounds theoxide layer 314, and thus, at least the insulating layer 619 and theoxide layer 314 separate surfaces of the substrate 302 from anysemiconductor dies 626 and/or interconnections 1044 and prevent contacttherebetween.

Similarly, in FIG. 12M, the metal cladding layer 315 is formed on allsurfaces of the substrate 302. However, unlike the oxide layer 314, themetal cladding layer 315 is coupled to at least one cladding connection1290 forming at least one connection point on at least one side of thepackage 1200, or as shown in FIGS. 12N-12M, a cladding connection 1290forming at least one connection point on both sides 677 and 675. Thecladding connections 1290 are connected to a common ground used by oneor more the semiconductor dies disposed with the package 1200.Alternatively, the cladding connections 1290 are connected to areference voltage, such as a power voltage. As depicted, the claddingconnections 1290 are formed in the insulating layer 619 and connect themetal cladding layer 315 to connection ends of the cladding connections1290 that are disposed on or at the surface of the package 1200, such asmajor surfaces 1007 and 1005, so that the metal cladding layer 315 canbe connected to an external common ground or reference voltage (shown inFIG. 12N as an exemplary connection to ground. The cladding connections1290 are formed of any suitable conductive material, including but notlimited to nickel, copper, aluminum, gold, cobalt, silver, palladium,tin, or the like. The cladding connections 1290 are deposited or platedthrough cladding vias 633 that may be formed at operation 522 and aresubstantially similar to the contact holes 632. Accordingly, thecladding vias 633 may be laser drilled through the insulating layer 619directly above or below the substrate 302 having the metal claddinglayer 315 formed thereon. Furthermore, like the interconnections 1044,the cladding connections 1290 may completely fill the cladding vias 633or line the inner circumferential walls thereof, thus having a hollowcore. In some embodiments, the cladding vias 633 have a diameter about 5μm.

To further clarify the grounding function of the metal cladding layer315 and the cladding connections 1290, FIG. 12N schematically depictsthe package 1200 of FIG. 12M simultaneously stacked with two electronicsystems 1295, 1296 and coupled to exemplary ground 1299 (3D integrationof the reconstituted substrates 1000 and/or packages 1200, however, isdescribed in greater detail with reference to FIGS. 13A-20F below).Although depicted as being connected to ground 1299, the metal claddinglayer 315 may alternatively be connected to, for example, a referencevoltage as described above. Each electronic system 1295, 1296 includes a2D or 3D circuit that includes traces, interconnection wiring, andtypically one or more electrical devices. In some embodiments, theelectronic system 1295, 1296 include one or more electrical device thatform part of an electrical system, such as a SIP, SIC, or SOC, which caninclude one or more semiconductor devices 1297, 1298, respectively. Asshown, the semiconductor device 1297 is electrically coupled tointerconnections 1044 adjacent to the major surface 1007 of the package1200 and the semiconductor device 1298 is electrically coupled tointerconnections 1044 adjacent to the major surface 1005. Deviceconnections 1297A, 1298A (which may include interconnections andredistribution connections) of the semiconductor devices 1297, 1298,respectively, may be coupled with the interconnections 1044 orredistribution connections 1244 via any suitable structures and methods,including solder bumps or balls 1246.

Simultaneously, the metal cladding layer 315 may be electrically coupledto external ground 1299 via the cladding connections 1290 and any othersuitable coupling means. For example, the cladding connections 1290 maybe indirectly coupled to external ground 1299 via solder bumps 1246 onopposing sides of the package 1200. In some embodiments, the claddingconnections 1290 may be first routed through a separate electronicsystem, such as electronic system 1295, before coupling to the externalground 1299. The utilization of a grounding pathway between the metalcladding layer 315 and the external ground 1299 reduces or eliminatesinterference between interconnections 1044 and/or redistributionconnections 1244 and prevents shorting of integrated circuits coupledthereto, which may damage the semiconductor dies 626, package 1200, andany systems or devices integrated therewith.

FIG. 13 illustrates a flow diagram of a representative method 1300 offorming an exemplary stacked 3D structure 1400 having two verticallystacked reconstituted substrates. FIGS. 14A-14D schematically illustratecross-sectional views of the stacked 3D structure 1400 at differentstages of the method 1300 depicted in FIG. 13. Thus, FIG. 13 and FIGS.14A-14D are herein described together for clarity. Further, the methodsdepicted in FIGS. 13 and 14A-14D and described below involve a build-uptechnique to form the stacked 3D structure 1400. Accordingly, suchmethods may be referred to as “build-up stacking.”

The method 1300 begins at operation 1302 and FIG. 14A wherein a firstinsulating film 1416 is placed on a desired surface of a reconstitutedsubstrate 1000 a to be integrated with another device, such as anotherreconstituted substrate, and thereafter laminated. The reconstitutedsubstrate 1000 a may include all of the features described above withreference to the reconstituted substrate 1000, including a structuralframe formed from a substrate 302 a having cavities 305 a and vias 303 apatterned therein.

As depicted in FIG. 14A, the insulating film 1416 is placed on the majorsurface 1007 having a single redistribution layer 1258 a formed thereon.Generally, the insulating film 1416 is placed on a surface of thereconstituted substrate 1000 a having exposed interconnections, such asredistribution connections 1244 a, that are conductively coupled to thecontacts 630 a on the active surfaces 628 a of the semiconductor dies626 a and/or interconnections 1044 a. Though depicted as having a singleredistribution layer 1258 a, the reconstituted substrate 1000 a may havemore or less than one redistribution layer formed on any desiredsurfaces thereof. Furthermore, the method 1300 may be utilized to 3Dintegrate structures other than the reconstituted substrate 1000 a, suchas the intermediary die assembly 602. Still further, prior to placementand lamination of the insulating film 1416, the reconstituted substrate1000 a may be secured on a carrier, such as the carrier 624, formechanical support during any of the operations of the method 1300.

The insulating film 1416 is substantially similar to the insulatingfilms 616 and 1216 and may include one or more flowable layers 1418formed of polymer-based dielectric materials and one or more protectivelayers 1422 formed of, for example, PET. In one embodiment, the flowablelayer 1418 includes an epoxy resin material, such as aceramic-filler-containing epoxy resin material. In another embodiment,the flowable layer 1418 includes a polyimide material, such as aphotosensitive or non-photosensitive polyimide material. In still otherembodiments, the flowable layer 1418 includes a PBO material, a silicondioxide material, and/or a silicon nitride material.

In some examples, the material of the flowable layer 1418 is differentfrom the material of the flowable layer 618 and/or the flowable layer1218. In other examples, the flowable layer 1418 includes the samematerials as the flowable layer 618 and/or the flowable layer 1218.

The insulating film 1416 has a total thickness of less than about 80 μm,such as between about 10 μm and about 60 μm. For example, the insulatingfilm 1416 including the flowable layer 1418 and the protective layer1422 has a total thickness of less than about 120 μm, such as betweenabout 20 μm and about 40 μm. The flowable layer 1418 itself may have athickness between about 5 and about 50, such as a thickness betweenabout 10 and about 25.

Upon placement of the insulating film 1416, the reconstituted substrate1000 a is exposed to a lamination process substantially similar to thelamination processes described above with reference to operations 508,516, 740, and 1102. The reconstituted substrate 1000 a is exposed toelevated temperatures to soften the flowable layer 1418 of theinsulating film 1416, which subsequently bonds to the major surface 1007of the reconstituted substrate 1000 a (e.g., with the redistributionlayer 1258 a). The flowable layer 1418 thus becomes integrated with theinsulating layer 619 of the reconstituted substrate 1000 a and forms abase layer 1410 for any devices and/or structures to be stacked directlythereon. The base layer 1410 covers any exposed interconnections on thesurface it is bonded to, such as the redistribution connections 1244 aon the major surface 1007, and provides a substantially planar structureupon which additional devices may be formed.

In one embodiment, the lamination process at operation 1302 is a vacuumlamination process that may be performed in an autoclave or othersuitable device. In one embodiment, the lamination process is performedby use of a hot pressing process. In one embodiment, the laminationprocess is performed at a temperature of between about 80° C. and about140° C. and for a period between about 1 minute and about 30 minutes. Insome embodiments, the lamination process includes the application of apressure of between 10 psig and about 100 psig while a temperature ofbetween about 80° C. and about 140° C. is applied to the substrate 302and insulating film 1216 for a period between about 1 minute and about30 minutes. For example, the lamination process is performed at apressure of between about 30 psig and about 80 psig and a temperature ofbetween about 100° C. and about 120° C. for a period between about 2minutes and about 10 minutes. For example, the lamination process isperformed at a temperature of about 110° C. for a period of about 5minutes. In further examples, the lamination process is performed at apressure between about 30 psig and about 70 psig, such as about 50 psig.

After lamination, the protective layer 1422 is mechanically removed fromthe base layer 1410 and the reconstituted substrate 1000 a is ready tohave another device stacked thereon (e.g., vertically integratedtherewith).

In the exemplary embodiment depicted in FIG. 13 and FIGS. 14A-14D, thereconstituted substrate 1000 a is stacked with a second reconstitutedsubstrate 1000 b by build-up stacking, wherein the second reconstitutedsubstrate 1000 b is built up directly over the reconstituted substrate1000 a in a manner substantially similar to the operations describedwith reference to methods 500 and 900. Thus, for clarity, onlyoperations 1304 and 1306 will be described in further detail, as theremaining operations of method 1300 are described above with referenceto methods 500 and 900.

At operation 1304, a second structured substrate 302 b is placed uponthe base layer 1410 formed on the reconstituted substrate 1000 a. Thesecond structured substrate 302 b may include any desired featurespatterned therein, including vias 303 b for formation ofinterconnections therethrough and cavities 305 b for placement ofsemiconductor dies therein. In some embodiments, the substrate 302 bfurther includes an oxide layer 314, such as a silicon oxide film formedon desired surfaces thereof for insulation. During placement, thesubstrate 302 b is aligned with the reconstituted substrate 1000 a suchthat vias 303 b formed in the substrate 302 b are aligned with contactpoints of the redistribution connections 1244 a or interconnections 1044a. In some embodiments, the substrate 302 b may be placed over the baselayer 1410 such that the vias 303 b are disposed directly above theinterconnections 1044 a and/or redistribution connections 1244 a.

At operation 1306, one or more semiconductor dies 626 b are placedwithin the cavities 305 b formed in the substrate 302 b. As describedabove, the cavities 305 b may have any desired lateral dimensions andgeometries, thus enabling placement of different types of semiconductordevices and/or dies in any desired arrangement for heterogeneous 3Dintegration. Accordingly, the one or more semiconductor dies 626 placedin the cavities 305 b may be of the same type or of different types fromeach other and/or the semiconductor dies 626 embedded within thereconstituted substrate 1000 a.

Furthermore, the semiconductor dies 626 within each reconstitutedsubstrate 1000 a and 1000 b may be of the same or different types andhave different shapes, dimensions, and/or arrangements. Generally, evenif the semiconductor dies 626 in each reconstituted substrate 1000 a or1000 b are of different types and/or have different shapes, dimensions,and/or arrangements, the lateral dimensions of the reconstitutedsubstrates 1000 a, 1000 b (e.g., the substrates 302 a, 302 b) are stillsubstantially the same to enable build-up stacking. However, it iscontemplated that reconstituted substrates of different lateraldimensions may be stacked together by the build-up stacking methodsdescribed herein.

After placement of the dies 626 b within the cavities 305 b (i.e., FIG.14C), operations 512-522 of the method 500 and operations 910-970 of themethod 900 are performed to the substrate 302 b at operation 1308 toform a completed reconstituted substrate 1000 b over the reconstitutedsubstrate 1000 a, thus forming the 3D stacked structure 1400. Forexample, an insulating layer is formed around the substrate 302 b byplacing, laminating, and curing an insulating film substantially similarto films 616 and 1416 over the substrate 302 b. A flowable layer of theinsulating film may flow into the vias 303 b and the cavities 305 b andintegrate with the base layer 1410 and insulating layer 619 uponlamination, thus forming an extension of the insulating layer 619.Accordingly, the insulating layer 619 may be described as being extendedto substantially surround both the substrate 302 a and the substrate 302b to form a singular and integrated 3D device structure.

Upon the formation of an insulating layer around the substrate 302 b,the substrate 302 b has one or more interconnections 1044 b formedtherein. Similar to the processes described above, one or morethrough-assembly vias are laser-drilled through the vias 303 b, nowfilled with the extended insulating layer 619. The drilling ofthrough-assembly vias in the substrate 302 b exposes contact points(e.g., top surfaces) of the redistribution connections 1244 a and theinterconnections 1044 a of the reconstituted substrate 1000 a below,enabling the interconnections 1044 b to be formed in direct contact withthe redistribution connections 1244 a and the interconnections 1044 a.

Therefore, after exposing the underlying conductive features by laserdrilling, interconnections 1044 b may be formed in (e.g., by growing orplating conductive material) directly over and in contact with theredistribution connections 1244 a and the interconnections 1044 a,eliminating any need for the utilization of intermediary electricalcoupling structures between the reconstituted substrates 1000 a and 1000b, such as solder bumps or contact pads.

The interconnections 1044 b formed through the reconstituted substrate1000 b are formed by any suitable methods including electroplating andelectroless deposition. In some embodiments, the interconnections 1044 bcompletely fill the through-assembly vias and contact holes in whichthey are formed or only cover inner circumferential walls thereof. Forexample, the interconnections 1044 b may line the inner circumferentialwalls of their corresponding through-assembly vias and have hollowcores. In some embodiments, the interconnections 1044 b are formed ofcopper. In other embodiments, the interconnections 1044 b may be formedof any suitable conductive material including but not limited toaluminum, gold, nickel, silver, palladium, tin, or the like. Further,the interconnections 1044 b may be formed of the same or differentconductive material than the interconnections 1044 a and/orredistribution connections 1244 a of the reconstituted substrate 1000 b.In some embodiments, the material of the interconnections 1044 b of thereconstituted has a different grain size than the material of theinterconnections 1044 a and/or the redistribution connections 1244 a.

In some embodiments, after interconnection formation, one or moreredistribution layers 1258 b having redistribution connections 1244 bmay be formed upon the reconstituted substrate 1000 b. Accordingly, theformation of the reconstituted substrate 1000 b results in a fullyfunctional stacked 3D structure 1400 that vertically integrates thereconstituted substrates 1000 a, 1000 b, depicted in FIG. 14D. Thus,after formation of the stacked 3D structure 1400, one or more additionaldevices may be stacked upon the 3D structure 1400 by build-up stackingor other stacking methods, or the 3D structure 1400 may be singulatedinto individual 3D packages or SiPs.

The devices and methods described above provide many advantages overconventional stacking arrangements and may be utilized in any suitableadvanced 2.5D or 3D integration application. In one exemplary embodimentdepicted in FIG. 15A, the method 1300 is utilized to efficiently form 3Dstacked DRAM structures 1500 a-c in heterogeneous batches, with eachstacked DRAM structure 1500 a-c having a different grade of memory die1526 a-c embedded therein, respectively. Thus, during formation or thereconstituted substrates 1000, each grade of memory dies 1526 a-c issorted and placed in the same designated cavities formed in thesubstrate frames (e.g., substrate 302) of each reconstituted substrate1000. Upon forming the stack of the reconstituted substrates 1000,individual stacked DRAM structures 1500 a-c may then be singulated fromthe stacked reconstituted substrates 1000 to form individual stacks.Accordingly, the method 1300 may be utilized to achieve batch memorystacking, wherein each memory stack may comprise of only one type ofmemory die for performance matching. While not illustrated in FIG. 15A,in some embodiments, the singulated stacks may include two or moresilicon dies within a cavity 305 thereof.

In another exemplary embodiment, the stacked DRAM structures 1500 a-care integrated into high bandwidth memory (HBM) modules having largeparallel interconnect densities between memory dies and centralprocessing unit (CPU) cores or logic dies. Traditionally, HBM modulesinclude a flip chip DRAM die stack interconnected to a logic die by asilicon interposer and solder bumps. Bandwidth between the DRAM diestack and the logic die is therefore limited by the size of the solderbumps and the pitch therebetween, which is generally larger than about20 μm. A smaller pitch between memory die interconnections of an HBMmodule, however, is enabled by utilizing stacked memory dies, such asthe stacked DRAM structures 1500 a-c described above, and embedding theminto the cavity 305 of a larger reconstituted substrate 1000 along witha logic die, as illustrated in FIGS. 15b and 15 c.

As depicted in FIG. 15b , an HBM structure 1550 may include any of thestacked DRAM structures 1500 a-c embedded within the cavity 305 of thereconstituted substrate 1000. Alternatively, FIG. 15c illustrates an HBMstructure 1560 having an exemplary HBM flip chip stack 1570 in place ofthe DRAM structures 1500 a-c. The HBM flip chip stack 1570 generallycomprises a stack of DRAM memory dies 1572 communicatively coupled to acontroller die 1574, all interconnected by solder bumps 1576. To accountfor the thickness of the memory die stacks, the substrate 302 of thereconstituted substrate 1000 has a thickness less than about 900 μm,such as less than about 800 μm, such as for example, less than about 775μm. A pitch Pi between centers of the interconnections 1044 through thereconstituted substrate 1000 is between 150 μm and about 250 μm, such asabout 200 μm.

The DRAM structure 1500 a-c or HBM flip chip stack 1570 are embeddedwithin the cavity 305 alongside an active logic die 1528 and areinterconnected therewith by the interconnections 1044 and redistributionconnections 1244. Utilizing the methods described above, such as methods900 and 1100, a pitch PM of less than about 20 μm betweeninterconnections 1044 coupled to the contacts 1530 of the memory stacksas well as the interconnections 1044 coupled to the active logic die1528 is enabled. Thus, the density of the interconnections 1044 couplingthe DRAM structure 1500 a-c or the HBM flip chip stack 1570 with theactive logic die 1528 is increased, improving the performance of the HBMstructures 1550 and 1560.

Another exemplary embodiment of a stacked structure utilizing thedevices and methods described above is depicted in FIG. 16, where fourpackages 1200 are homogenously integrated by wafer-to-waferpolymer-copper hybrid bonding to form a stacked structure 1600. Asdepicted, each package 1200 includes a memory die 1526 embedded withinthe substrate 302 and encapsulated by the insulating layer 619 (e.g.,having a portion of each side in contact with the insulating layer 619).One or more interconnections 1044 are formed though the entire thicknessof each package 1200, which are directly bonded with one or moreadjacent packages 1200. Although memory dies 1526 are depicted, any typeof semiconductor device or die, such as semiconductor dies 626, may beutilized.

The wafer-to-wafer bonding of the packages 1200 may be accomplished byplanarizing the major surfaces 1005, 1007 of adjacent reconstitutedsubstrates 1000 (prior to singulation) or packages 1200 (aftersingulation) and placing the major surfaces 1005, 1007 against oneanother while applying physical pressure, elevated temperatures, or anelectrical field to the packages. Upon bonding, the one or moreinterconnections 1044 and/or redistribution connections 1244 of eachreconstituted substrate 1000 or package 1200 directly contact one ormore interconnections or redistribution connections of an adjacentreconstituted substrate 1000 or package 1200, thus forming electricallyconducting paths that may span the thickness or height of the entireDRAM structure 1600. One or more solder bumps 1246 may then be plated ordeposited over the interconnections 1044 and/or redistributionconnections 1244 for further integration with other systems and/ordevices.

Wafer-to-wafer bonding of the packages 1200 enables the stacking ofsemiconductor dies 626 differing in size and without the utilization ofsolder bumps, providing a CTE-matched stack since both the semiconductordies 626 and the substrates 302 are made of silicon. The close-proximitystacking of individual packages 1200 further provides a rigid structurethat reduces or eliminates warping and/or sagging thereof. Withoutsolder bumps, copper interconnections 1044 of individual packages 1200may also be directly coupled to each other, thus reducing or eliminatingreliability issues associated with intermetallic reactions caused bysolder bumps.

FIGS. 17A-17B illustrate additional exemplary stacked structures 1700 aand 1700 b similar to stacked structure 1600. Unlike stacked structure1600, however, one or more interconnections 1044 are directly in contactwith one or more solder bumps 1246 disposed between major surfaces 1005and 1007 of adjacent (i.e., stacked above or below) packages 1200. Forexample, as depicted in the stacked structure 1700 a, four or moresolder bumps 1246 are disposed between adjacent packages 1200 to bridge(e.g., connect, couple) the interconnections 1044 of each package 1200with the interconnections 1044 of an adjacent package 1200. Theutilization of solder bumps 1246 enables the stacking of semiconductordies, packages, and/or reconstituted substrates having the same ordifferent lateral dimensions. FIG. 17A illustrates four stacked memorydies 1526 and packages 1200 having substantially the same lateraldimensions, while FIG. 17B illustrates two stacked packages 1200 withmemory dies 1526 having different dimensions.

The utilization of solder bumps 1246 to bridge interconnections 1044 ofadjacent packages 1200 further creates a space (e.g., distance) betweenthe insulating layers 619 thereof. In one embodiment, these spaces arefilled with an encapsulation material 1748 to enhance the reliability ofthe solder bumps 1246. The encapsulation material 1748 may be anysuitable type of encapsulant or underfill. In one example, theencapsulation material 1748 includes a pre-assembly underfill material,such as a no-flow underfill (NUF) material, a nonconductive paste (NCP)material, and a nonconductive film (NCF) material. In one example, theencapsulation material 1748 includes a post-assembly underfill material,such as a capillary underfill (CUF) material and a molded underfill(MUF) material. In one embodiment, the encapsulation material 1748includes a low-expansion-filler-containing resin, such as an epoxy resinfilled with (e.g., containing) SiO₂, AlN, Al₂O₃, SIC, Si₃N₄,Sr₂Ce₂Ti₅O₁₆, ZrSiO₄, CaSiO₃, BeO, CeO₂, BN, CaCu₃Ti₄O₁₂, MgO, TiO₂, ZnOand the like. In some embodiments, the encapsulation material 1748 has athickness corresponding to the diameters of the solder bumps 1246.

In one embodiment, the solder bumps 1246 are formed of one or moreintermetallic compounds, such as a combination of tin (Sn) and lead(Pb), silver (Ag), Cu, or any other suitable metals thereof. Forexample, the solder bumps 1246 are formed of a solder alloy such asSn—Pb, Sn—Ag, Sn—Cu, or any other suitable materials or combinationsthereof. In one embodiment, the solder bumps 1246 include C4 (controlledcollapse chip connection) bumps. In one embodiment, the solder bumps1246 include C2 (chip connection, such as a Cu-pillar with a solder cap)bumps. Utilization of C2 solder bumps enables a smaller pitch betweencontact pads and improved thermal and/or electrical properties for thestacked structure 1700. In some embodiments, the solder bumps 1246 havea diameter between about 10 μm and about 150 μm, such as a diameterbetween about 50 μm and about 100 μm. The solder bumps 1246 may furtherbe formed by any suitable wafer bumping processes, including but notlimited to electrochemical deposition (ECD) and electroplating.

FIG. 18 schematically illustrates an efficient method of formingindividual stacked memory (e.g., DRAM) structures 1800 a-c utilizingsolder bumps 1246 instead of build-up stacking methods, similar tostacked structure 1700 a. As depicted, desired memory dies 1526 areembedded within reconstituted substrates 1000 and stacked utilizingsolder bumps 1246 to provide coupling between interconnections and/orredistribution connections of each reconstituted substrate 1000. In theexemplary embodiment shown in FIG. 18, the memory dies 1526 in eachreconstituted substrate 1000 are arranged within die stacks 1026,previously described with reference to FIGS. 10I-10K and the method 900.It is also contemplated that the memory dies 1526 may be individualplaced or arranged in a side-by-side configuration with additionalmemory dies 1526 in each cavity of the reconstituted substrates 1000.After a desired number of reconstituted substrates 1000 are stacked withthe solder bumps 1246, individual stacked DRAM structures 1800 a-c maybe singulated therefrom, thus enabling batch memory stacking with solderbumps 1246.

The stacked structures and methods described above generally includeembedded semiconductor dies and devices having substantially the samevertical orientation, wherein active surfaces thereof face the samedirection or side of the stacked structure. It is further contemplated,however, that semiconductor dies and other devices may be embeddedwithin the above-described structures having differing (e.g., opposite)orientations. FIG. 19 illustrates a flow diagram of a representativemethod 1900 of forming an exemplary stacked 3D structure 2000 whereinembedded semiconductor dies or other devices have different verticalorientations between different layers (e.g., levels). FIGS. 20A-20Fschematically illustrate cross-sectional views of the stacked 3Dstructure 2000 at different stages of the method 1900. Thus, FIG. 19 andFIGS. 20A-20F are herein described together for clarity. As with themethod 1300, the methods depicted with reference to FIGS. 19 and 20A-20Fmay also be described as “build-up stacking.”

Generally, the method 1900 begins at operation 1902 and FIG. 20A whereina base layer 2010 is formed on a desired surface of the reconstitutedsubstrate 1000 a to be integrated with another layer of devices. Thereconstituted substrate 1000 a may include all of the features describedabove, including a structural frame formed from a silicon substrate 302a and having cavities 305 a and vias 303 a patterned therein. The baselayer 2010 is substantially similar to the base layer 1410 and may beformed of the same materials and by the same methods described abovewith reference to FIGS. 13 and 14A-14D.

As depicted in FIG. 20A, the base layer 2010 is formed over the majorsurface 1007 having a single redistribution layer 1258 a thereon. Thoughdepicted as having a single redistribution layer 1258 a, thereconstituted substrate 1000 a may have more or less than oneredistribution layer formed on any desired surfaces thereof. Generally,the base layer 2010 is formed on a surface of the reconstitutedsubstrate 1000 a corresponding with the side towards which activesurfaces 628 a of semiconductor dies 626 a are facing (e.g., orientedtowards). In the present example, the active surfaces 628 a are orientedtowards the side 677 of the substrate 302 a.

At operation 1904 and FIG. 20B, a structured substrate 302 b is alignedand placed upon the base layer 2010 formed on the reconstitutedsubstrate 1000 a. Generally, the structured substrate 302 b hasdimensions substantially the same as the substrate 302 a of thereconstituted substrate 1000 a. As described with reference to themethod 1300, the second structured substrate 302 b may include anydesired features patterned therein, including vias 303 b and cavities305 b. In some embodiments, the substrate 302 b further includes anoxide layer 314 or metal cladding layer 315. During placement, thesubstrate 302 b is aligned with the reconstituted substrate 1000 a suchthat vias 303 b formed in the substrate 302 b are aligned with contactpoints of the redistribution connections 1244 a or interconnections 1044a.

At operation 1906, one or more singulated packages 1200, each having oneor more semiconductor dies 626 b, are placed within the cavities 305 band are thereafter laminated. As depicted in FIG. 20C, the singulatedpackages 1200 are placed in the cavities 305 b with active surfaces 628b of the semiconductor dies 626 b facing the base layer 2010, thereforebeing in an orientation opposite that of the active surfaces 628 a. Aspreviously described, the cavities 305 b may have any desired lateraldimensions and geometries to enable placement of packages 1200 havingdifferent types of semiconductor devices and/or dies therein.Accordingly, the semiconductor dies 626 b may be of the same type or ofdifferent types from each other and/or the semiconductor dies 626 aembedded within the reconstituted substrate 1000 a. It is furthercontemplated that in certain embodiments, intermediary die assemblies602 may be placed within the cavities 305 b in place of the singulatedpackages 1200, or in addition thereto.

Upon lamination of the packages 1200 within the substrate 302 b, aninsulating layer 2019 is formed over the packages 1200 and the substrate302 b at operation 1908 and FIG. 20D. The insulating layer 2019 issubstantially similar to the insulating layer 619, and may be formed ofthe same materials and by the same methods described above. Accordingly,formation of the insulating layer 2019 over the substrate 302 results inany unoccupied cavities 305 b and vias 303 b of the substrate 302 bbeing filled with insulating dielectric material, as well as thepackages 1200 being embedded within the substrate 302 b.

At operations 1910-1912 and FIGS. 20E-20F, one or more interconnections1044 c are formed through the dielectric-filled vias 303 b and connectedwith interconnections 1044 a or redistribution connections 1244 a of thereconstituted substrate 1000 a. Additionally, new redistributionconnections 1244 c may be formed in the insulating layer 2019 to rerouteinterconnections 1044 b of the packages 1200. Prior to metallization,one or more through-assembly vias 603 and/or redistribution vias 1203are laser-drilled through the dielectric material of the insulatinglayer 2019, packages 1200, and/or base layer 2010, similar to theprocesses described above. The drilling of through-assembly vias 603and/or redistribution vias 1203 exposes contact points (e.g., topsurfaces) of the interconnections 1044 a, redistribution connections1244 a, and/or interconnections 1044 b, enabling the interconnections1044 b and/or redistribution connections 1244 c to be formed in directcontact therewith. Thus, after exposing the underlying conductivefeatures by laser drilling, the interconnections 1044 c may be formed in(e.g., by growing or plating conductive material, as described inembodiments above) directly over and in contact with the redistributionconnections 1244 a and the interconnections 1044 a, eliminating any needfor the utilization of intermediary electrical coupling structuresbetween the reconstituted substrate 1000 a and the packages 1200integrated above, such as solder bumps or contact pads. Upon completionof operation 1912, one or more additional redistribution layers may beformed and/or devices stacked over desired surfaces of the stackedstructure 2000.

The stacked structures 1400, 1500 a-d, 1600, 1700 a-b, 1800 a-c, and1900 provide multiple advantages over conventional stacked structures.Such benefits include thin form factor and high die-to-package volumeratio, which enable greater I/O scaling to meet the ever-increasingbandwidth and power efficiency demands of artificial intelligence (AI)and high performance computing (HPC). The utilization of a structuredsilicon frame provides optimal material stiffness and thermalconductivity for improved electrical performance, thermal management,and reliability of 3-dimensional integrated circuit (3D IC)architecture. Furthermore, the fabrication methods for through-assemblyvias and via-in-via structures described herein provide high performanceand flexibility for 3D integration with relatively low manufacturingcosts as compared to conventional TSV technologies.

In sum, the embodiments described herein advantageously provide improvedmethods of reconstituted substrate formation and wafer-to-wafer stackingfor fabricating advanced integrated semiconductor devices. By utilizingthe methods described above, high aspect ratio features may be formed onglass and/or silicon substrates, thus enabling the economical formationof thinner and narrower reconstituted substrates for 2D and 3Dintegration. The thin and small-form-factor reconstituted substrates andreconstituted substrate stacks described herein provide the benefits ofnot only high I/O density and improved bandwidth and power, but alsomore economical manufacturing with dual-sided metallization and highproduction yield by eliminating single-die flip-chip attachment, wirebonding, and over-molding steps, which are prone to feature damage inhigh-volume manufacturing of integrated semiconductor devices.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method of forming a stacked semiconductordevice, comprising: placing a first dielectric film over a semiconductorpackage, the semiconductor package comprising: a first semiconductor diedisposed within a first cavity of a first silicon substrate and embeddedwithin a first insulating layer, the first insulating layer disposedover a first side and a second side of the first silicon substrate andcontacting each side of the first semiconductor die; and a firstconductive interconnection disposed within a first via of the firstsilicon substrate and extending from at least the first side to thesecond side of the first silicon substrate, wherein the first insulatinglayer is disposed between the first conductive interconnection andsurfaces of the first via; positioning a second silicon substrate overthe first dielectric film, the second silicon substrate comprising asecond cavity and a second via formed therein; placing a secondsemiconductor die within the second cavity formed in the second siliconsubstrate; laminating the first and second dielectric films to form asecond insulating layer, the second insulating layer embedding thesecond semiconductor die within the second cavity; and forming a secondconductive interconnection within the second via.
 2. The method of claim1, wherein forming the second conductive interconnection comprises:laser ablating a hole in the second insulating layer disposed within thesecond via; and forming a metal layer over a surface of the hole in thesecond insulating layer.
 3. The method of claim 2, wherein the formingthe second conductive interconnection further comprises: forming amolybdenum adhesion layer and a copper seed layer over the surface ofthe hole prior to forming the metal layer.
 4. The method of claim 2,wherein the laser ablation exposes a surface of the first conductiveinterconnection through the hole, and wherein the second conductiveinterconnection is electrically coupled to the first conductiveinterconnection.
 5. The method of claim 2, wherein the forming the metallayer comprises electroplating or electroless deposition.
 6. The methodof claim 2, wherein the second conductive interconnection extends atleast from a first surface to a second surface of the second siliconsubstrate.
 7. The method of claim 1, wherein the first and the secondsemiconductor dies are of different types.
 8. The method of claim 1,wherein the first and the second semiconductor dies are of the sametype.
 9. The method of claim 8, wherein the first and secondsemiconductor dies are DRAM dies and the stacked semiconductor device isa stacked DRAM device.
 10. The method of claim 1, wherein the firstinsulating layer and the second insulating layer comprise the samematerial.
 11. The method of claim 10, wherein the first insulating layerand the second insulating comprise an epoxy resin material havingceramic fillers.
 12. The method of claim 1, wherein the secondinsulating layer comprises a polyimide material.
 13. A method of forminga stacked semiconductor device, comprising: placing a first dielectricfilm over a semiconductor package, the semiconductor package comprising:a first plurality of semiconductor dies disposed within one or morefirst cavities of a first silicon substrate and embedded within a firstinsulating layer, the first insulating layer disposed over a first sideand a second side of the first silicon substrate and contacting eachside of each of the first plurality of semiconductor dies; and a firstplurality of conductive interconnections disposed within a firstplurality of vias of the first silicon substrate and extending from atleast the first side to the second side of the first silicon substrate,wherein the first insulating layer is disposed between the each of thefirst plurality of conductive interconnection and surfaces of the firstplurality of vias; positioning a second silicon substrate over the firstdielectric film, the second silicon substrate comprising one or moresecond cavities and a second plurality of vias formed therein; placing asecond plurality of semiconductor dies within the one or more secondcavities formed in the second silicon substrate; laminating the firstand second dielectric films to form a second insulating layer, thesecond insulating layer embedding the second plurality of semiconductordies within the one or more second cavities and filling each of thesecond plurality of vias; laser ablating a plurality of holes in thesecond insulating layer, each of the plurality of holes formed through aportion of the second insulating layer filling one of the secondplurality of vias; and forming a second plurality of conductiveinterconnections, each of the second plurality of conductiveinterconnections formed over a surface of one of the plurality of holes.14. The method of claim 13, wherein the forming the second plurality ofconductive interconnections further comprises: forming a molybdenumadhesion layer and a copper seed layer over the surfaces of each of theplurality of holes.
 15. The method of claim 13, wherein the laserablation exposes a surface of at least one of the first plurality ofconductive interconnections through the plurality of holes, and whereinat least one of the second plurality of conductive interconnections iselectrically coupled to the at least one first conductiveinterconnection.
 16. The method of claim 13, wherein the forming thesecond plurality of conductive interconnections comprises electroplatingor electroless deposition of the second plurality of conductiveinterconnections.
 17. The method of claim 13, wherein at least one ofthe second plurality of conductive interconnections extends at leastfrom a first surface to a second surface of the second siliconsubstrate.
 18. The method of claim 13, wherein at least one of the firstplurality of semiconductor dies and at least one of the second pluralityof semiconductor dies are of different types.
 19. The method of claim13, wherein at least one of the first plurality of semiconductor diesand at least one of the second plurality of semiconductor dies are ofthe same type.
 20. A method of forming a stacked DRAM device,comprising: placing a first dielectric film over a semiconductorpackage, the semiconductor package comprising: a first DRAM die disposedwithin a first cavity of a first silicon substrate and embedded within afirst insulating layer, the first insulating layer disposed over a firstside and a second side of the first silicon substrate and contactingeach side of the first DRAM die; and a first conductive interconnectiondisposed within a first via of the first silicon substrate and extendingfrom at least the first side to the second side of the first siliconsubstrate, wherein the first insulating layer is disposed between thefirst conductive interconnection and surfaces of the first via;positioning a second silicon substrate over the first dielectric film,the second silicon substrate comprising a second cavity and a second viaformed therein; placing a second DRAM die within the second cavityformed in the second silicon substrate; laminating the first and seconddielectric films to form a second insulating layer, the secondinsulating layer embedding the second DRAM die within the second cavityand filling the second via; laser ablating a hole in the secondinsulating layer filling the second via; and forming a second conductiveinterconnection over a surface of the hole.